Troubleshooting Hard Disk Drives

This section includes troubleshooting information for a wide variety of hard disk problems. Hard disk problems can range from outright failure to data corruption to problems with setup. Since they are so important--they hold your main data--hard disk problems can be particularly unnerving, and I have tried to include as much information as possible to help you with problems related to them.

You should not hesitate to contact your hard disk drive manufacturer's technical support department if you need them. In my experience these companies have above-average technical support, and there are sometimes problems specific to certain kinds of drives that I do not know about and therefore are not listed here.

Explanation: There is a general failure of the hard disk. Either an error message is being displayed indicating a failed disk at boot time, or some other wholesale problem is either preventing access to the hard disk, preventing it from booting, or making it impossible to detect the drive in the BIOS setup program. If the drive won't boot but is accessible after booting from a floppy, look here.

Diagnosis: There are many different causes of apparent hard disk failures. Sometimes the problem is the disk itself, but just as often it is a configuration or other problem.

Recommendation:

• The first thing to check for is whether or not the hard disk can be seen by the hard disk controller; usually on a true hard disk failure, the disk will not be detectable by the controller (but this is not always the case). Assuming you have an IDE hard disk, enter the BIOS setup program and use the IDE detection facility of the BIOS to see if the disk's parameters can be detected. If the disk cannot be autodetected using the autodetect feature in the BIOS program then you should continue here for more troubleshooting of the disk and controller themselves. Failure to detect the disk usually implies immediately some sort of hardware problem. Note that SCSI disks are set up through the SCSI controller, but here again, you need to see if the disk is recognized.
• If you can see the hard disk when you autodetect, the problem is more likely to be software than hardware. Remember that you cannot usually boot a brand new hard disk until it has been partitioned and formatted.
• See if the disk will boot up. If it will not boot, then boot from a floppy boot disk and then use the FDISK command (or other partitioning software) to see if you can see the disk. If you can see the drive, continue here.
• If the drive will boot up, then you should be getting a more specific error message of some sort, or a more specific failure mode that you can use for troubleshooting. Look here for error messages.
• If the drive is detected in the BIOS setup but cannot be booted or accessed when booting from a floppy disk, then there is a good chance that the disk itself may be bad. I would, if possible, try connecting the hard disk to another system and see if the problem is present there as well. If so, I would contact technical support for the hard disk, because the drive may be bad. If the problem goes away, then there is something wrong with the setup in your PC that is causing the hard disk to misbehave. If you've exhausted other options, you may want to read through the troubleshooting section for when the drive cannot be detected. Some of the problem causes here can also be responsible for problems even when the drive can be seen by the BIOS, though they are less common in this situation.
• If the hard disk is dead and you have a concern about data on it, look here.

Explanation: You have a hard disk that was working properly in an existing PC but stopped working when installed in a new PC (or after upgrading the motherboard or making another similar change).

Diagnosis: There are many different reasons why this sort of thing can happen. Often, it is simply an installation or configuration problem that can plague any PC after it has been worked on. However, it is also possible that there is an incompatibility between how the two BIOSes access the disk. In particular, BIOSes can use different translation modes to access the disk sectors. So it may be the case that the new PC is referring to the sectors on the disk in a different order than the old one was, which can cause many problems. The use of dynamic drive overlays can also complicate matters, especially if you are moving from a system that does not have native BIOS translation support, to one that does.

Recommendation:

• Try troubleshooting the hard disk by looking back in the hard disk troubleshooting index and diagnosing the specific problem you are having (hard disk not recognized, won't boot, etc.) It is possible that a configuration, setup or cabling issue is what is at fault, and the disk will work properly once it is fixed.
• Make sure that the new hard disk is set up with the correct translation mode in the BIOS setup of the new PC.
• If you were using a dynamic drive overlay on your previous PC, you may have a problem when you move to a new machine that has native BIOS support, because the new system may enable translation when the overlay is expecting it to be turned off. One option is to go into the BIOS setup and turn off translation support by setting up the hard disk as "Normal" instead of "LBA", "Large" or whatever. However, this is not a great solution, since you are keeping the drive overlay when you don't have to. Instead, you should remove the drive overlay, and set up the disk with native large-disk support.
• If you want to be safe, then perform a full backup of the disk before transferring it to the new system. Then, detect, setup, partition and format the disk on the new system, and transfer the contents back to the disk again. This of course is not without its risks also (the backup medium could fail, so be very careful) but will ensure that the disk is being set up in the correct new environment

Explanation: The hard disk drive is refusing to boot when the system is started. After a bootable floppy disk is used, however, the hard disk can be seen and accessed using disk utility software such as FDISK or Partition Magic.

Diagnosis: Usually, if the disk can be detected in the BIOS setup and accessed after booting from the floppy disk, this implies a software problem of some sort. A common one is a boot sector virus. Another common problem is trying to boot up a new hard disk before partitioning and formatting it.

Recommendation:

• Try rebooting the hard disk again. If it doesn't boot up, then try resetting the PC and seeing if it boots now. If it does, then you should continue here.
• On an existing hard disk, make sure that you scan the disk well with a current virus scanner. Some boot sector viruses can make it impossible to boot the disk. Then, when you boot from the floppy, you end up bypassing the virus and the disk is visible.
• Make sure that if you are setting up a disk or changing its partitions around using FDISK, that you set the boot partition "active" or bootable. Otherwise the primary partition cannot be booted.
• If this is a brand new hard disk that you just installed into the PC as the primary master (boot) drive, you will not be able to boot it because there are no disk structures on the disk to allow the operating system to boot. You must boot the operating system from a floppy disk, and then partition and format the disk before using it.
• It is possible that there is a corrupted boot sector or other major disk structure, if we are talking about an existing drive. Look here for ideas about this.
• If you are trying to set up a dual-boot configuration, you may need to put the DOS partition as the first partition on the drive. Setting it active may not be sufficient; it may need to reside physically first on the disk to boot properly

Explanation: The hard disk drive cannot be detected using the autodetect utility within the BIOS setup program. Usually, the BIOS will pause for a long time while it searches for the drive, and then will return saying that the drive was not found.

Diagnosis: There are many, many different reasons why a hard disk may not be visible to the BIOS setup program. They usually fall into two major categories: problems with configuration (how the drives are set up) and problems with the drive itself. There are occasionally problems with the hard disk controller, but these are less common.

Recommendation:

• If this is a new hard disk, or a hard disk moved into a new system, or the system was just built or upgraded, I'd recommend reading this section that discusses common problems when setting up or working on new systems.
• If you have another system that you can try the drive in, it is a good idea to connect it to the other PC and see if it will be detected there. Bear in mind that moving the disk to a new PC can introduce other variables that might confuse the issue, but I have seen this be a very effective way to isolate the trouble to either the hard disk or the PC. Similarly, if you try another identical (or even just similar) disk in place of the one not working, that can tell you if the problem is the drive or the hard disk controller (of course, the drive could just be jumpered incorrectly; see below for more). If the hard disk controller is implicated, troubleshoot it here.
• You should determine if the hard disk has power and is spinning up. The only reliable way to do this is to take the cover off the PC and listen as you turn the power on. You should be able to hear the hard disk spin up. If it spins up and then spins back down again immediately, this is a sign of a problem with the disk itself. If it doesn't spin up at all, then either the drive is dead, or there is a problem with the power connection to the drive. Make sure the power input connection to the disk is tight. Try swapping it with a different power connector and see if the drive comes up. If other peripherals don't have power either this could be a power supply problem. Sometimes hard disks will not spin up if there isn't sufficient power at startup. This can happen especially with older power supplies.
• If the disk is SCSI, you need to check all of the various parts of the SCSI chain. The SCSI host adapter (controller) must be checked to ensure that it is working properly. The hard disk and all other devices on the SCSI chain must have a different device ID. The termination must be set up correctly. See here for more details on SCSI configuration.
• If the disk is on an IDE channel with another drive (hard disk or CD-ROM), then you should try the disk by itself on the channel. You may need to change the jumpers on the drive to do this, but you definitely need to try the drive without the complicating factor of another device on the channel. If the disk works by itself but not when set up with another drive, you may have a master/slave conflict. (Note that sometimes there actually is no conflict; the drive may not have been jumpered correctly, and you may have inadvertently fixed this when the configuration was changed).
• Make sure that the hard disk is configured properly. The jumpers should be set correctly. The ribbon cable should be inserted properly and pin 1 on the drive should be matched up with pin 1 on the hard disk controller or motherboard.
• If you had a master and a slave drive on the IDE channel and removed one of the two drives, the one that remains may need to be rejumpered. Some hard disks--for example those manufactured by Western Digital--use different jumpers for when they are a master with a slave drive present vs. when they are alone on a channel. If you leave a WD drive jumpered as master when it is alone on the channel, it may not boot, or may boot only after a long delay. Other manufacturers' drives may work just fine this way, however.
• Make sure that if you are using only one controller, that the ribbon cable for the drive is connected to the correct IDE port on the motherboard or controller. If you connect it to the secondary channel's port instead of the primary channel's, then the disk may not be detected.
• Make sure that the IDE controller is enabled; on modern systems the IDE controllers are enabled or disabled using BIOS settings. It is common for the secondary controller to be disabled; if you are adding a hard disk to the secondary channel you will need to enable the channel. The primary IDE channel should of course also be enabled if the primary channel is being used.
• Watch out for conflicts between built-in IDE controllers and add-in controllers. If you are using an add-in controller, for example for enhanced BIOS translation support, then you need to make sure you disable the built-in controller so that there is no conflict. Watch out for sound cards that have IDE controllers built in to them--this is quite common. Make sure the controller is not enabled unless you are using it.
• There could be a problem related to the IDE cable. If you have another IDE cable, try replacing the existing one and seeing if this solves the problem. Try a shorter cable if possible; long cables sometimes cause problems. Make sure that the IDE cable is not being stretched or crimped.
• Some BIOSes fail very ungracefully when they are presented with a disk that has a geometry including over 4,096 cylinders (over 2.1 GB). In some cases they will fail to detect the drive at all (others may have a problem with these larger disks but they will at least notice that the disk is there). Some BIOSes apparently handle 2 GB disks OK but choke on hard disks over 4 GB. You should investigate your motherboard's characteristics to find out if there are any known limitations.
• Some very old hard disks may not autodetect at all; they may just not work on your system. This is quite unusual and not encountered often with modern hardware.
• I have seen a hard disk lock up and not be able to be recognized by the system in some circumstances when paired with a CD-ROM drive on an IDE channel.
• Believe it or not, some older Compaq PCs used proprietary hard disks. You could not just plug in any old IDE hard disk and expect it to work. If you have an older Compaq (386 class) then you may want to contact their technical support about a hard disk for it.
• If after trying all of the above the hard disk still appears to be dead, you should contact the technical support department of the drive's manufacturer for more assistance. Sometimes there are special situations that arise that the technical support people may be able to help you with--for example, a drive may have a known problem for which there is a workaround. You may also want to inquire about the possibility of a replacement drive if it is still under warranty.

• If the hard disk is dead and you have a concern about data on it, look here.

Explanation: The hard disk is supposed to be dynamically autodetected by the BIOS when the system boots, but the system does not detect it. It either hangs the boot process at the stage where the IDE drive should be autodetected, or it says that there is no disk connected (possibly after a long pause while it searches for the device.)

Diagnosis: One possibility is that the BIOS settings to enable boot-time autodetection are not correct. If the settings are correctly entered, then there is a problem either with the hard disk or with its connection to the hard disk controller or motherboard. (Note that some older drives will not autodetect properly at all, but we're talking very old equipment here.)

Note: SCSI hard disks are detected and set up differently. You will need to consult your SCSI controller documentation for help with problems related to SCSI devices.

Recommendation:

• Enter the BIOS setup program and attempt to manually autodetect the hard disk in question. This will test to see if the hard disk can be seen by the hard disk controller. If the disk cannot be autodetected using the autodetect feature in the BIOS program then you should continue here for more troubleshooting of the disk and controller themselves.
• Assuming that the hard disk will autodetect in the BIOS, and you want it to autodetect at boot time, make sure that the disk type is set to "Auto" (the actual settings and values may vary by system, but this is the most common).
• Make sure that the disk really isn't being autodetected at boot time. It is possible that the BIOS may autodetect the drive but just not report what it finds when the system boots. Check the system configuration summary that prints when the BIOS boots. If the disk is listed there correctly then even if there is no report about the detected drive at boot time, it is being detected (assuming that the BIOS setting is correct.)
• It is possible that if the hard disk is being sought at boot time too quickly, the hard disk isn't ready when the BIOS tries to access it.
• If the system will still not autodetect the drive at boot time, I would suspect a problem with the hard disk controller and troubleshoot it.
• It is possible that there is a more general problem with the motherboard, but that is unlikely.

Explanation: There appears to be a failure of some sort with the hard disk controller. On modern systems the (IDE) hard disk controller is built into the motherboard; on an older system it is typically found as an expansion card. It is easy to tell which type you have by looking to see where the IDE cables go that are connected to the hard disk.

Diagnosis: Actual failures of the hard disk controller are relatively rare; usually the problem is either one of configuration and installation, or is actually the hard disk itself that is causing the problem.

Recommendation:

• If your PC uses a separate hard disk controller, check all the connections to it. Try removing it from its slot and reinserting it; sometimes the card may not be seated properly and this will fix it. If possible, try switching the controller with another one and see if that fixes the problem.
• If you just installed an add-in controller, make sure that it is jumpered correctly and set up to control the correct IDE channel. For example, you may have the add-in controller set to act as the primary, secondary or tertiary IDE channel. If you installed it into a PC that also has integrated controllers, make sure that those controllers are disabled or you may have a conflict if they both try to operate the same channel number.
• Check for resource conflicts with the controllers on a built-in PC. They usually use IRQ 14 and IRQ15, and some devices may conflict with these, such as SCSI host adapters and network cards.
• Watch out for sound cards that have built in IDE controllers that may be enabled even if you don't want them. Read the directions and make sure that the controller on the sound card is disabled so it does not conflict with other hardware, if you are not using it. Most Sound Blaster and compatible sound cards do have these controllers.
• Bus mastering drivers can cause problems with older controller cards. They just may not work properly at all. See here for more on IDE bus mastering driver problems.
• It is possible that there is a configuration or jumpering problem with one or more IDE devices that is causing this problem. I would follow this troubleshooting section that talks about how to diagnose a hard disk that cannot be detected, because many of the causes of that problem and this one are the same.
• If the IDE controllers are built into the motherboard, there is a possibility of a motherboard problem (this is unusual, but could occur). You might want to troubleshoot the motherboard.

Explanation: The system will only boot the hard disk after a warm reset is performed when it is powered on for the first time. It will not boot the first time that the power is turned on.

Diagnosis: There are many possible reasons for a hard disk that fails to boot. If a warm reset consistently fixes the problem, however, then this implies that the system is trying to boot the hard disk before it is ready to operate. It takes several seconds for hard disks to come up to speed when they are first turned on, since they must spin up to speed, and then several internal calibrations and tests are often performed. Older BIOSes took thirty seconds or more to complete their power-on tests and boot the operating system, but newer ones can do this in ten seconds or less. Some of these BIOSes are smart enough to wait for the hard disk to signal that it is ready and then will boot, but older ones may hang up.

Recommendation:

• Some systems have a BIOS setting to allow you to delay the booting of the hard disk by several seconds to alleviate this problem. If you have a boot delay setting then enable it and see if that fixes the problem.
• Use other BIOS settings to make the initial boot-up take longer. For example, many BIOSes have a "Quick Boot" setting that speeds up the boot process by skipping some of the power-on tests. Disabling this will make the bootup take longer. Enabling "Floppy Drive Seek" will also cause the boot to take a few seconds longer. There may be other options as well, depending on your system.
• If an upgrade is available, you may want to consider upgrading your system BIOS.
• There could be a different cause of this problem; troubleshoot the hard disk here.
• Replace the hard disk with another model that comes up to speed more quickly.

Explanation: Windows 95 is booting up saying that it is using compatibility mode for the hard disk.

Diagnosis: This problem is usually caused by misconfiguration, particularly old drivers that are left over after an upgrade from an older operating system.

Recommendation:

• Scan the system for viruses. Viruses can cause compatibility mode to be used.
• Make sure the hard disk(s) are physically configured correctly.
• If you are using a dynamic disk overlay (like Disk Manager), make sure you are using a version that is designed for use with Windows 95. Older versions can cause this problem.
• Make sure there are no hard-disk-related drivers being loaded in the system CONFIG.SYS or AUTOEXEC.BAT files.
• You may have an incorrect or incompatible set of bus mastering drivers installed. This will cause Windows 95 to use compatibility mode. See here for more help on bus mastering drivers

Explanation: You have a system with both IDE/ATA and SCSI hard disks installed, but the system insists on booting the IDE hard disk before the SCSI one. Since the SCSI hard disk (usually) has higher performance (often because it uses more advanced technology) it is preferable to boot from the SCSI drive instead of the IDE one.

Diagnosis: Unfortunately, there is no resolution to this problem in many cases. IDE/ATA hard disks are natively supported by the BIOS on most PCs, while SCSI hard disks are not. For this reason, the BIOS is programmed to look first for IDE hard disks and boot them if any are found. The SCSI drives are not looked at until afterward. There are now some newer motherboards (namely the Asus boards) that have a BIOS that will allow you to select booting from SCSI ahead of IDE on a system that has both. Most motherboards do not allow this.

Recommendation:

• Go into the BIOS setup program, and look for an option to boot from SCSI first in the boot sequence BIOS setting. You may or may not find this, depending on your system (most do not have it, unfortunately).
• Check the motherboard or system manufacturer's web site for a possible BIOS upgrade that will allow booting SCSI first (it is unlikely that you will find one, however).
• Replace the motherboard with another one that will allow booting from SCSI first. While this may seem radical, given the cost of SCSI peripherals this is not a very expensive move (although it certainly is a pain).
• Remove the IDE/ATA hard disk from the system. If there is no IDE/ATA hard disk in the system, the SCSI disk should boot. (Obviously, this is less than ideal if you wanted to use both disks)

Explanation: A hard disk that has important data on it has been diagnosed as being dead. The disk cannot be accessed through normal means to recover the data that is on it, but that data must be retrieved.

Diagnosis: Due to the enormous amount of important data that is not backed up regularly and is therefore lost to failed hard disks every year, special companies have sprung up that specialize in performing special heroics on dead drives to access and retrieve data on disks that under normal circumstances would never be readable again. This process is called data recovery. These companies are expensive, and there are sometimes steps you can perform yourself instead of hiring them, although you need to carefully weigh your options before touching your drive and make sure of what you are attempting. These companies are professionals and their success rate is actually pretty high.

Warning: Make absolutely sure that the disk is really dead before you try anything at all in this section. I am assuming that you have diagnosed it properly and also contacted your manufacturer's technical support department. If you aren't sure, don't touch the drive.

Warning: Tinkering with a dead drive can (and often will) void your warranty. If the drive is under warranty, contact the manufacturer's technical support department about data recovery options before you try anything that involves altering the drive. If you alter the drive then the manufacturer may have no choice but to not honor the warranty, since they will have no way of knowing if the problem was indeed caused by your working on the disk.

Recommendation: Assuming that your disk is dead and you want to try "extreme measures" to try to get it running again, try some of the above. Note that if you do manage to get the disk going again, make sure that you will have some other drive set up to pump the data to. You may only get the disk running again once; don't miss the opportunity to save the data:

• Some drive failures are actually failures of the integrated controller board, and if you swap this board with an identical one from another drive, you may be able to get the drive working. You can only do this with a spare board from an identical board. Contact your manufacturer about the availability of replacement logic boards. If you feel daring and have a second of the exact same hard disk you may be able to "borrow" its board for the test. Needless to say, this is tricky business so proceed with caution.
• Older drives, from around 1990 or before, often fail by refusing to spin up at all. If this is the case, sometimes it is caused by the spindle motor getting "stuck", and manually spinning the motor up will allow the drive to spin free long enough to get the data off of it. I have even opened up older (1985 era) hard disks and spun them manually to get them running. These older disks will tolerate running for a short time with the cover off (the clean room environment inside the drive is important, but can be violated if the air is relatively clean and if the drive is only going to be pumped and then discarded). The idea is simple: open up the disk and manually move the platters--don't touch the platters, rotate the hub in the middle--and then turn the disk on and it may spin up. Empty the disk to another device and then throw the disk out. It can work--but it is a very risky thing to do and will void the warranty on any disk you try it on (it's only generally needed on old disks though). Also, it only generally helps on very old disks that are physically jammed and thus won't spin up at all when the power is applied. If the disk is spinning then this fix does not apply, and I've never tried it on a newer drive.
• On rare occasions, simply retrying booting up the hard disk many times may cause a hard disk with a serious but intermittent problem to "revive" once to allow it to be pumped. This does not happen often, but may be worth a try. Turning the system on and off a lot is hard on other components of the system, so go easy, and disconnect whatever you can before you start. Always wait at least 15 seconds after turning off a PC before turning it back on again.
• Contact a data recovery company and ask them for an assessment. Shop around, because some of these companies are much more competitive than others. See this section for details on PC repair and dealing with repair shops

Explanation: You bought and installed a hard disk but the system is seeing it as smaller than it actually is supposed to be.

Diagnosis: This is not really a problem at all, but actually a discrepancy in the way drive sizes are reported. Hard disk manufacturers use decimal megabytes (1,000,000 bytes) in their advertising, and BIOS auto-detect routines use the same measure. Other software, especially most disk setup and partitioning utilities like FDIS, use binary megabytes (1,048,576) in their reporting. The difference of about 5% is what you are seeing.

Recommendation: 

• Read the more complete discussion of binary and decimal storage measurements here in the Reference Guide.
• See this reference table for a listing of the difference in size between decimal and binary measures

Explanation: You are noticing that while your hard disk is supposed to be able to hold a certain amount of data, say 2 GB, that it becomes full despite having several hundred megabytes of less data stored on it. You may also notice for example that you have a volume with 100 MB of free space but you are unable to copy 90 MB of files to it before the disk becomes full.

Diagnosis: It is very common to encounter this, especially on larger disks. In most cases there is really nothing wrong, except that a substantial portion of the storage area of the disk is wasted. In addition, various software packages can consume large amounts of hidden storage. File system corruption can legitimately lead to lost storage space.

Recommendation: "Missing" free space on a hard disk is often caused by a combination of different causes. Try all of the following, since you may find that more than one applies:

• The most likely cause of this observation is simply that you have probably lost a good deal of your disk space to what is called slack. Since the FAT file system allocates space in chunks called clusters, each file can only use a whole number of clusters. This means that if you create a 1,000-byte file in a volume that uses 16,384-byte clusters, 15,384 bytes are wasted. Multiply that by thousands of files and this is the cause of many people's missing space problems. Slack is discussed in much more detail here.
• Scan the hard disk for file system corruption. You should check for file system problems regularly as part of your system care routine. Various problem situations can cause clusters on the hard disk to be marked as used when no file is using them, and that space is then legitimately "missing". Fixing the lost clusters will free up this space. Usually only a small number of clusters are lost at a given time. If you see lost clusters regularly, troubleshoot that problem here.
• Discrepancies in storage totals of 5-10% are often a result of the fact that some software uses binary megabytes and gigabytes to measure storage, and other software uses decimal megabytes and gigabytes. See here for a more complete discussion.
• If you are using a disk drive that is over 2.1 GB in size and you are not using Windows 95 OEM SR2's FAT32 file system, your hard disk must be broken into multiple partitions to get full use of the disk. Sometimes vendors will do this without telling their customers about it, so you may know that you bought a 3.2 GB drive but only be able to see 2.1 GB of it. In this case, look for another drive letter (typically D:, E: etc.) where you should be able to see the rest of your hard disk.
• Software that is designed to protect against accidental file deletion works by storing files you delete in a hidden area on the disk, so that if you later regret deleting them, you can restore them easily. Windows 95's Recycle Bin does this. Norton Utilities and other programs add more hidden areas where deleted files are stored. If you don't carefully monitor the settings on these programs, they can chew up a lot of disk space with files you thought you had deleted. Windows 95 is smart enough to offer to empty the Recycle Bin when the disk gets full; I am not sure what Norton does. At any rate, right-clicking on the Recycle Bin should yield an option to let you empty the Bin, which may free up some space. If you are using Norton's Unerase or Protection, be particularly wary of it using large amounts of disk space for its protection routines, and cut back on how much of the disk it is allowed to use.
• If you are trying to copy a large number of files (over 500) to the root directory of a drive volume you will find that you cannot, despite having a lot of space on the disk. This is because the root directory is limited in size. Regular directories are not limited, so try putting the files in a subdirectory.
• If you have created a compressed volume then part of the host drive will be used to contain the compressed volume file. For example, if you have a 1 GB C: partition and use 400 MB of it to create a 700 MB compressed volume called D:, then C: will of course have 400 MB taken to hold the compressed volume.
• Compressed volumes themselves only estimate the amount of free space on a volume, because they cannot know how much will fit on the disk until the files are copied there (since different files compress different amounts).
• If you try to create more than one primary DOS partition on a hard disk using a utility like Partition Magic, or if you have a non-DOS partition on the disk such as a UNIX partition, that space will be hidden from view when you are running DOS or Windows.

Explanation: You put a new hard disk in your system and transferred the information from your older, smaller hard disk to the new one, only to find that the same files are taking up significantly more room.

Diagnosis: The usual cause of this problem is that the larger disk is using a larger cluster size. Under the FAT file system only whole clusters can be assigned to a file, so the larger the cluster size, the more space that is wasted; this is called slack. If you have 3,000 files taking up 300 MB of space on a 340 MB hard disk, then on average, 12 MB of that is wasted space due to the cluster size. Transferring that same data to a new 1 GB hard disk (partitioned in a single volume) will cause the same files to take up about 312 MB of space because the cluster size on the new disk will be 16 KB instead of 8KB.

Recommendation:

• Don't worry about it. I mean, if you just upgraded from a 300 MB disk to a 2 GB disk and now your 300 MB takes up 312 MB or even 350 MB, so what? A 2 GB disk costs about $200 today, making 100 MB of disk space, purchased as part of a 2 GB disk, worth about 10 bucks.
• If you want to reclaim the lost hard disk space, partition your larger disk into several smaller partitions. Read this part of the Reference Guide that discusses tradeoffs in selecting partition sizes.
• Upgrade to Windows 95 OEM SR2, which includes the FAT32 file system that lets you create large volumes with small cluster sizes. First, read about the tradeoffs in using FAT32 here

Explanation: The system is not seeing the full size of your hard disk. In particular, the system is detecting the disk as being either 504 or 528 megabytes (depending on what piece of software is reporting the size). Other than this, the hard disk does appear to work.

Diagnosis: The maximum size of an IDE/ATA hard disk running in standard, untranslated mode is 504 binary megabytes, or 528 decimal megabytes. This is the classic barrier that limits the use of larger hard disks on older systems. In order to use a disk over 504 MB in size, you must have a motherboard or hard disk controller capable of BIOS translation, or you must use a dynamic drive overlay to do the translation in software. If your large disk is showing up as 504/528 MB, then this means that either your motherboard and BIOS do not have translation support, or that support has not been enabled.

Recommendation:

• When you see this smaller size of your disk, make sure you are looking at the whole disk and just a partition of it. If the disk has been broken into several partitions then of course each will appear smaller than the disk itself. To check the size of the physical disk as detected by the system, use the BIOS setup program or a disk utility like FDISK.
• Check in your BIOS setup program for a hard disk setting like "Translation Mode". You are looking for a setting that you can set to something like "LBA", "Large" or "ECHS". These are BIOS translation modes. If you cannot find any setting like this, the chances are that your motherboard does not support BIOS translation. If the BIOS date is from July 1994 or later, it should have translation support for large hard disks built into your BIOS, but older ones usually do not.
• If your motherboard has translation support, make sure it is turned on. Most motherboards automatically enable translation when they detect a larger hard disk, but some BIOSes do not do this properly. It is also possible that if you put a newer disk in place of an old one, that the old standard mode is still set in the BIOS. You will usually want a disk larger than 504 MB to be in "LBA" mode, since this is the de facto standard translation mode for large disks.
• If you do not have native translation support, you will have to add it to the system in order to allow full access to the disk. There are several ways to do this, generally involving either an upgrade to the BIOS or hardware, or the use of a software drive overlay. This section of the Reference Guide discusses adding translation support to a system.

Explanation: There is a hard disk over 2.1 GB in size being used in a system that supports BIOS translation. The disk's size is being presented as either truncated to only 2.1 GB, or it is showing up as a much smaller number like 400 MB for a 2.5 GB drive.

Diagnosis: The most likely cause of this problem is that while your BIOS supports translation, it is not correctly handling disks that have over 4,096 cylinders. There were some BIOSes that did not handle these larger disks correctly; this is one of the hard disk size barriers. Different BIOSes handle these larger disks differently when they aren't supported properly. Some simply truncate the disk to 4,096 cylinders so that the disk appears to be 2.1 GB in size, and others "wrap around" so that they show up as 400 MB (2.5 GB minus 2.1 GB). This is discussed here.

Tip: If this disk is showing up as 504 MB or 528 MB, this is a sign that BIOS translation is not functioning on the machine. Continue here.

Recommendation:

• Make sure that you are really seeing how much of the disk is being detected, and not just one of the partitions. In particular, there is a 2 GB partition size limitation under the FAT file system, which means you cannot make any disk volume greater than 2 GB even if the BIOS does detect all 2.5 GB of a 2.5 GB drive. See here for more on this limitation.
• You will need to "fix" your system's ability to handle these larger disks. In some cases, a BIOS upgrade may do the trick; contact your motherboard manufacturer.
• See this discussion of overcoming hard disk size barriers. If your hard disk is being "wrapped around" then you may be able to make use of a special jumper on the hard disk that will make it appear to your system as only a 2.1 GB disk. This wastes some of the space on the disk, so it is far from ideal.
• Contact your motherboard manufacturer for more ideas.

Explanation: You are trying to configure two hard disks on the same IDE channel, with one as master and one as slave, but they are not working together properly. Generally, the system will not boot when they are both in the system, or only one of the drives is recognized by the BIOS. Each of the drives will work individually on the channel. You may find that drive A works as master to drive B as a slave, but drive A can't be a slave to drive B as the master.

Diagnosis: Problems getting drives to cooperate as master and slave are common when using drives made by different manufacturers if either of the drives was designed and manufactured before around 1994. Before this time there was not a generally agreed-upon set of standards for master and slave drives working together on the same channel, and problems were common. With two newer drives, problems with putting them on the same channel points more likely to configuration problems. Problems with two drives from the same manufacturer likewise implicates the drives or their configuration, since the manufacturers weren't generally stupid enough to make their own drives not work together.

Recommendation:

• Double-check the configuration of both drives. Make sure that they are both jumpered correctly and connected to the same channel, that pin 1 of the cable is lined up correctly to pin 1 of the connector on both drives and the controller/motherboard.
• Independent master/slave device timing is a chipset feature that allows drives on the same channel to be set to different PIO modes. If you are using an older drive with a newer one, and your motherboard does not support independent timing, make sure that both drives are set to use a timing mode no faster than what is supported by the slower drive, or the slow one will not work properly.
• If the drives are not working together at all, consider changing the order and making the one that was previously the master into the slave, and vice-versa. This may not be acceptable to some people but for others will work.
• If you are using a manufacturer's brand of dynamic disk overlay (the free software hard disk manufacturers include to allow access to the full hard disk volume on machines without BIOS support for large disks) then you may have a problem when trying to add another manufacturer's large disk to the same IDE channel. The free versions of this software are generally tailored to work with a specific manufacturer's drives.
• Consider changing the way you set up your IDE devices; see this section for ideas on different ways to set them up. For example, if you have a new, fast hard disk, an older, slow hard disk and a CD-ROM drive, and you can't get the two hard disks to work together on the primary IDE channel, try putting the slow disk with the CD-ROM on the secondary channel. This is in some ways a more optimal arrangement in any event and may solve the conflict.
• You just may not be able to use the two disks on the same channel. You will be forced to change one disk or the other, or run them on separate channels

Explanation: You are trying to configure a new (or old!) hard disk on your system. You don't know what the drive geometry is, and your BIOS is old and doesn't provide autodetection capabilities.

Diagnosis: Usually you can find the information you are looking for (cylinders, heads, sectors) by looking on the web page of the manufacturer of the drive.

Recommendation:

• Look on the web page of the manufacturer of the disk for setup parameters for the drive.
• If you have access to another PC that does have the ability to autodetect, you can "borrow" it, autodetect to see what the parameters are, and then enter them manually into your BIOS

Explanation: You have a large hard disk, over 2 GB typically, and want to set it up as a single partition, but the system is restricting you to 2 GB maximum (or less).

Diagnosis: The normal limit on partition size in DOS, Windows 3.x and Windows 95 is 2 binary gigabytes, which is about 2.15 decimal gigabytes; this is a limitation of the conventional FAT16 file system. You can use all of a disk that is larger than this (assuming your BIOS will support the disk or you use another way of overcoming the 504 MB disk size barrier) but you must make each partition no larger than 2 GB. The only way around this is using the FAT32 file system available as part of Windows 95 OEM SR2.

Recommendation:

• First, if you are trying to partition your hard disk but it is showing up as being either 504 MB or 528 MB in size, or some other small number, then you have a different problem. This is caused by the BIOS being unable to properly support the hard disk due to its size. Look here for help with the 504/528 MB problem.
• If you have Windows 95 OEM SR2 installed then use its FDISK program, and enable "Large disk support" when asked. This will cause any partitions it creates in that session to be formatted as FAT32. Look here if you are having problems getting FAT32 to work. Look here for tradeoffs in using FAT32.
• If you have a hard disk over 2 GB in size and don't have Windows 95 OEM SR2 installed, you will have to partition the disk so each partition is smaller than 2 GB in size. (In fact, you may want the partitions to be even smaller than this for efficiency reasons; see this section discussing efficient partitioning tradeoffs)

Explanation: You have a modern motherboard that contains a primary and secondary IDE controller. You want to disable the secondary controller and do so by changing the BIOS setting that controls it. However, Windows 95 keeps redetecting and re-enabling the secondary IDE controller despite its being disabled.

Diagnosis: This problem is caused by the drivers that Windows 95 uses to support PCI controllers. You may have to manually remove the driver for the secondary controller under Windows 95. In some cases you won't be allowed to remove the secondary controller driver because it will say that the secondary controller is "part of a multifunction device" driver that contains the primary and secondary controller drivers. You must change a setting on this "parent" device to disable the secondary controller. If you just remove the parent device then Windows will redetect both primary and secondary controllers again.

Note: If you have any other IDE controllers in the system, such as one that is part of a sound card, it will also show up, usually as "Standard IDE/ESDI Hard Disk Controller". Just ignore it.

Recommendation:

• Check the obvious: make sure that you really did disable the secondary controller in the BIOS setup.
• Remove the secondary controller by changing the appropriate setting of the parent IDE controller device in the Device Manager.
• See this section in the Optimization Guide for more ideas on how to free up unneeded IDE channel resources

Explanation: A dynamic disk overlay has been installed to permit access to a large hard disk volume on a PC without BIOS support for large disks. The disk normally works fine, but under certain circumstances the disk cannot be accessed, or appears to the system as being only 504 MB in size (528 decimal megabytes).

Diagnosis: A dynamic disk overlay is a driver that is loaded very early in the boot process. This piece of software acts as the translation facility for a BIOS that doesn't have one built-in, allowing access to a large hard disk on a system that would otherwise be limited to 504 MB per disk. If anything happens to cause the overlay not to be loaded during the boot process, problems will result. Common culprits are booting from a floppy disk that wasn't made using the dynamic drive overlay software and also viruses.

Recommendation:

• Scan the system for viruses to make sure that it is clean.
• Beware of booting the system from boot floppies unless they have been specially prepared using your dynamic drive overlay software, which should be able to create boot disks that contain the overlay to allow you to boot from a floppy disk and still access your hard disk. It is recommended that you have at least two of these boot floppies created by the dynamic drive overlay software.
• If you want to boot a regular bootable floppy, you should start the system with the floppy released from the floppy disk and boot the hard disk first. The overlay will print a message telling you to press a key (such as the space bar) if you want to boot from the floppy disk. Then insert the floppy and boot it.

Note: If you need to boot the system clean to get rid of a virus, booting the hard disk first in this manner will be self-defeating, but booting a regular floppy disk straight will not allow proper access to the hard disk. This is why you need a boot floppy that includes your drive overlay

Explanation: There is a problem with the dynamic disk overlay software being used to allow access to the full contents of a larger hard disk on an older PC.

Diagnosis: Dynamic disk overlays are really kludges, pieces of software that are trying to act as mediator between a disk drive and a BIOS that can't properly support it. They work fine in most cases but there can be many different reasons why they have problems under various circumstances.

Recommendation:

• Troubleshoot the problem, as it is manifesting itself, by looking for the symptoms elsewhere in this section on troubleshooting hard disks. You may find the answer there.
• If you are using one of the specially-customized pieces of software created for one of the popular hard disk manufacturers, contact the manufacturer for technical support.
• The most commonly-used DDO is Ontrack's Disk Manager. Consult the Ontrack web site, which contains a great deal of troubleshooting material.

Explanation: The compressed disk volumes on the system cannot be seen after booting the PC from a floppy disk.

Diagnosis: Compressed disks require a driver in order for them to be properly accessed. If you are booting a disk that does not contain the correct compression driver, or if you are booting from an older version of DOS, you will not be able to see your compressed volumes because the correct driver software is not being loaded.

Recommendation:

• Do not boot from floppy disks that don't allow access to your compressed disks.
• Create new bootable floppies after booting the system that has the compressed volumes on it. This should cause recent versions of DOS to include the compression driver on the bootable disk, avoiding this problem in the future

Explanation: Disk compression was installed on the system and a compressed volume created. Using this volume now seems slower than it was before.

Diagnosis: This is a common side effect of using compression and is generally more often the rule than the exception. Compression works by adding a software interpretation layer and this takes processing time compared to just writing the data directly. The slowdown is especially noticeable on PCs with slower processors. On faster processors, compression can in theory improve overall performance by reducing the number of accesses to the (slow) hard disk. Compression performance is discussed in detail in this section of the Reference Guide.

Recommendation:

• Many compression programs, such as DriveSpace 3 for Windows 95, allow you to tweak the compression level that they use when storing files. You may be able to improve performance (at the cost of the compression level) by changing the compression level settings.
• Use compression only for applications and data for which performance is not a critical issue. Use multiple partitions and put items requiring top performance in an uncompressed area.
• If performance is paramount, do not use compression. While I am not dead set against its use, I recognize that it was far more important in the world of the $300 340 MB drive (a few years ago) than in the world of the $300 4 GB drive (today, with prices continuing to drop rapidly)

Explanation: While checking the file system or while performing work using the compression utility, compression errors were discovered in one or more compressed volumes.

Diagnosis: Compression errors are usually either a flaw or incompatibility with the compression software, or a more generalized problem with the hard disk itself.

Recommendation:

• If you are using an older compression driver, meaning DoubleSpace (not DriveSpace, which is the later product) or an early version of Stacker, consider upgrading to a newer version. There are known bugs that were ironed out in later releases.
• There could be a file system problem with the host volume (the one holding the compressed volume file) so make sure to scan it.

Explanation: The system said I had a certain amount of space free on my compressed volume but when I tried to copy an amount of files that should have fit, the disk ran out of space before copying all the files.

Diagnosis: It is impossible to know exactly how much free space there is on a compressed volume. The reason is that the amount you can store on the volume depends on how much its contents can be compressed, but the system doesn't know what the right ratio is until after the files have been copied. Therefore, the compression driver only estimates the amount of free space on the drive. If you copy a bunch of files to the volume that don't compress very much, you will use up a disproportionate amount of the free space. This is discussed in much more detail here, including an example.

Recommendation:

• Make sure that any compressed volumes on your system have realistic estimated compression ratios. These dictate how much estimated free space is reported on the volume. If you tell the system to estimate a 2 to 1 compression ratio but the files you are storing only compress at 1.5 to 1, then you are going to run out of space faster than you expect on the drive.
• Don't copy files to a compressed volume that are already compressed or that will not compress very well. Some people think that they can compress a disk and then fill it with ZIP files, doubling the amount of information they can archive. Unfortunately, TANSTAAFL, and with compression, compressing a second time rarely accomplishes much.
• See this section, which describes other situations (unrelated specifically to compression) that can cause free space to appear to be missing on a disk volume. (Note that the cluster size of a compressed volume generally cannot be changed and usually is small enough that it is not a major source of lost space

Explanation: After adding a new hard disk drive, the letters that were previously assigned to partitions on the old hard disk changed.

Diagnosis: This is a residue of the way DOS assigns drive letters. As discussed in detail here, DOS (and Windows) assigns drive letters first to the primary partitions in all hard disks in the system, and then to the logical partitions after that. If you start with a disk containing a C: primary partition and a D: logical disk volume, adding a new hard disk with a primary partition will cause the logical on the first disk to be pushed to E:

Recommendation: When adding a second hard disk to an existing system, partition it so that it contains only logical drives. Do not create a primary partition at all. This will cause the drive letter order to be preserved

Explanation: A drive volume letter appears to be "missing" from the system. For example, there may be a C:, D: and E: drive but only C: and D: show up in Windows Explorer.

Diagnosis: Assuming that there isn't a fault with the hard disk itself, the problem here is likely that the drive letter has been hidden by the operating system for one reason or another.

Recommendation:

• Make sure that the drive letter really does exist, and there isn't a physical disk problem. If none of the drive letters of a physical disk are showing up, the problem is likely with the disk, so troubleshoot it.
• See if the drive letter shows up when you boot to plain DOS. If it does, then this is likely a hidden drive letter problem.
• If you try to set up a disk with two primary partitions, using something like Partition Magic (since this cannot be done with normal partitioning software like FDISK) then one of the partitions will be hidden when you boot up.
• If you've installed the "TweakUI" applet (part of Microsoft's "PowerToys" add-on for Windows 95) then you should open it and look under the "My Computer" tab. You will find a checkbox for every drive letter, which lets you hide that drive from the "My Computer" display and the Windows Explorer. Make sure nothing is being hidden here.
• If you are using disk compression, and you decided to compress all or most of the host drive, then the operating system may hide the host drive letter (since it would be full from containing the compressed volume, and therefore not useful). Compression software can also play tricks such as remapping or changing drive letters. You can unhide a hidden compressed volume host disk by running the compression software utility, which is normally called DriveSpace if you are using Microsoft's compression facilities

Explanation: After booting from a floppy disk, one or more of the hard disk volumes that are normally present on the system seems to disappear.

Diagnosis: This is usually caused by drivers that are on the hard disk being bypassed when the floppy disk is booted. Another culprit is the ever-present virus threat. Some particularly nasty viruses encrypt the hard disk structures; when the hard disk is booted they load and then "decrypt" the structures on the fly. When you boot from the floppy the virus is bypassed and the encrypted structures cannot be read by the system. (Obnoxious, isn't it?)

Recommendation:

• If you are using a dynamic drive overlay to access the full size of your hard disk, then booting from a regular boot floppy not prepared by the drive overlay software will cause the hard disk to disappear. Look here for more on this.
• Make sure that the system is clean of viruses. If you think that you have an encrypting virus of the sort described in the diagnosis above, you may need to use special procedures to remove it (these are quite rare, fortunately). Consult your antivirus software's documentation.
• FAT32 disk volumes are only supported by Windows 95 OEM SR2. If you boot an older version of Windows or DOS, either from a floppy or another disk partition, FAT32 volumes will not appear to the system.

Explanation: The hard disk (through disk checking utilities) is reporting that one or more of its sectors are bad. This may be on a new drive, or there may be bad sectors showing up on a drive that has been in a system for a while.

Diagnosis: Unsurprisingly, bad sectors are generally a real problem with a hard disk and usually imply a legitimate problem with the hard disk itself. There are configuration problems that may be responsible, and these are usually resolved pretty easily, however the usual problem is the drive itself. Bear in mind that IDE/ATA and SCSI drives, at least all of the ones produced in the last five years or so, use a technique called remapping or spare sectoring to hide bad sectors detected on the drive at the factory. A new hard disk should have zero bad sectors on it. An older drive may "grow" a bad sector or two now and again, however in many cases this is a harbinger of impending disaster with the disk. Take it as the warning sign it is.

Recommendation: The steps below discuss possible problems that can lead to a bad sector showing up. In addition to trying to eliminate the cause, you also should contact your hard disk manufacturer's technical support department (phone or web site) and inquire about a utility to remap the bad sector so it is hidden and replaced with one of the spares on the disk (fixing the cause of the bad sectors is important but that doesn't get rid of the ones that are already there in some cases):

• As soon as you see any bad sectors show up on a disk that contains data, make sure you back up the disk immediately, or you risk possible loss of your data. I would avoid making any significant changes to the software setup on the drive, or adding any new data to it, until you get the situation resolved.
• Make sure that you have not set the hard disk timing (PIO mode) too high for the drive. You may want to try reducing the timing and seeing if this resolves the problem. Make sure that if your system does not support independent device timing, that you do not have the PIO mode set for what is optimal for the faster of two devices, but too fast for the slower one.
• Make sure that you are not using an IDE cable that is too long. The specified maximum is 18 inches, but some drives need them to be even shorter than that to work properly. Try replacing the cable with a shorter one, if possible.
• If you are getting bad sectors on more than one disk in the system, or even after replacing the disk, then the problem lies somewhere other than the disk, most likely. Suspect incorrect BIOS settings, and I would troubleshoot the motherboard as well. It could even be bad power from the power supply.
• Some hard disks have firmware problems. In this case the manufacturer may make a firmware upgrade available for the disk; this is like a flash BIOS upgrade for your hard disk (except it is easier to install and is used only for fixing bugs). Check your manufacturer's web site for more information on this possibility. I know for example that this has happened with some of Western Digital's Caviar series hard disks and in many cases the firmware upgrade resolved the problem nicely.
• Try to make sure that you have eliminated any of the possible configuration gotchas that can lead to problems with bad sectors. If you do and are still getting more bad sectors showing up, the drive should be treated as imminently failing and you should contact your manufacturer's or system vendor's technical support department. If the drive is new or the system is still under warranty, insist on a replacement drive. See here for more. There is no reason for a new hard disk to have bad sectors on it, period. Don't let them try to convince you otherwise.
• If you have a drive out of warranty that gets one or two bad sectors, then if you feel comfortable with the drive, map out the bad sectors and continue using it. In some cases, there is just one weak area on the disk, and the rest of it will continue to be quite usable for some time. However, if the number of bad sectors is large or is increasing in time, look out, because the chances of the drive failing outright become much higher when this happens.
• On very old drives--meaning before IDE, the older drives from the mid-80s that used stepper motors--there is a phenomenon called "Monday morning blues" that can result in bad sectors showing up on hard disks. This occurs especially when the hard disks are cold, after being off overnight or over the weekend (thus the name). These stepper motor drives cannot compensate for thermal expansion of the disk platters and may not be able to read the tracks on the drive until the disk has warmed up. Waiting a half-hour may see the problem go away, but in the long run the disk will need to be low-level formatted again. (None of this applies to modern IDE or SCSI hard disks).

Explanation: The system detected an error trying to access a disk volume. The drive letter is specified in the error message and could be a hard disk, floppy disk, mapped network volume, etc.

Diagnosis: This sort of message on a hard disk can mean either file system corruption or bad sectors on the drive. It can also be caused by software or driver bugs, or by running out of system resources under Windows 3.x.

Recommendation:

• If you are using Windows 3.x, go the Program Manager, click "Help", then "About Program Manager". Check the number listed for system resources. If it is below about 20-30%, that may be the cause of your problem. Try rebooting and checking the value, to see if it increases, and see if the system runs better. I recommend rebooting Windows 3.x daily if it is heavily used. See here for more help on Windows 3.x system resources.
• If the volume being read is a floppy disk, this probably just means that the particular disk in the drive has developed errors. Try a different disk, or Troubleshoot the floppy disk drive(s).
• For a hard disk, scan for file system errors and then also perform a surface scan for bad sectors. If you find any bad sectors, diagnose them here. If the hard disk seems to be failing, troubleshoot it

Explanation: You attempted to read from a disk volume that wasn't ready to send data to the system.

Diagnosis: This is almost always caused by trying to read data from a removable storage device that has no media in it, such as an empty CD-ROM drive or floppy disk drive. If it occurs with a hard disk, this probably means the drive has a problem or is misconfigured.

Recommendation:

• If the drive is a hard drive, this almost always means a general failure of the disk. Troubleshoot the hard disk drive.
• For a floppy disk drive, troubleshoot this problem here.
• For a removable storage drive, place a disk into the drive and try the command again. Note that it may take several seconds for a CD-ROM drive to recognize an inserted disk

Explanation: While attempting to access a Western Digital hard disk using FDISK, a "Runtime error" is encountered.

Diagnosis: This error message means that there has been some corruption or damage to track zero (where key file system structures are stored).

Recommendation:

• Contact Western Digital technical support.
• Use Western Digital's low-level disk utility to clear the disk. Realize that this will wipe out the entire disk!

Explanation: The hard disk feels very hot while it is operating.

Diagnosis: It is normal for hard disks, especially newer ones, to feel hot while they are operating. They should not get as hot as solid-state components like processors; they will often feel warm to the touch but should not be uncomfortable to put a hand onto. Newer disks that spin at 7200 RPM or higher will tend to get hotter than older, slower drives. A properly-ventilated case should be able to handle all but the hottest drives without additional cooling measures being required.

Recommendation:

• Check the cooling level of the case as a whole if you suspect that the case is not being ventilated properly.
• You may want to change the physical layout of the inside of the case. If the hard disk is mounted close to another disk or other hot-running components, or in a place where it will not receive much air flow to cool it, moving it may reduce its temperature.
• High-performance disks such as Seagate's 10,000 RPM Cheetah often require special cooling arrangements. I recommend you contact the manufacturer directly for advice on cooling high-end, high-RPM disk drives

Explanation: The hard disk is causing a great deal of vibration as it spins while running.

Diagnosis: Hard disks, especially newer ones, do vibrate to some extent, although this should not be excessive. Better quality disks will normally have less vibration than cheaper ones. A disk that vibrates a great deal or that starts vibrating more than it did in the past may be headed for failure. On the other hand, some vibration is not a great concern.

Recommendation:

• Make sure that the hard disk is mounted securely and properly into the case. Ensure that four screws have been used to mount it, and that they are tightly secured (but not too tightly, or the drive could be damaged).
• If the case itself is cheaply made (using cheap aluminum sheet metal instead of a sturdier steel) then this will tend to allow more vibration.
• If a drive begins to rattle, or to vibrate much more than it ever did in the past, this could be a sign of pending failure (although it might not be). In particular, it is often a sign of bearings that are failing

Explanation: The activity LED on the system case flickers every few seconds, even when nothing is going on with the PC.

Diagnosis: There are a couple of possible explanations for this behavior. First is Windows 95's "auto-insert notification". The feature that automatically loads software from CD-ROM drives works by constantly checking to see if there is a CD-ROM disk in the drive. This causes the activity light to flicker on some systems. Another possibility is that there is system work occurring that you may not be aware of. Windows does do some housekeeping work at occasionally odd times, and there can also be background tasks that run from time to time.

Recommendation:

• Pay close attention to when the LED lights up. If it is regular, every three seconds or so, this is the auto-insert notification. If it is irregular or hard to track, then it is likely just periodic system activity, which is perfectly normal. For example, several seconds after closing a Windows application, Windows may rearrange its internal memory structures and you'll see it access the disk a great deal. (During normal activity you can usually hear the hard disk operating, as well, while the auto-insert-notification-induced LED lighting is not normally accompanies by any actual hard disk activity.)
• If you do not need auto-insert notification then disable it. This can be done from the Device Manager. Go into the Control Panel, select the System icon, then the Device Manager tab. Click on the "CDROM" icon to reveal the CD-ROM drive in your system, then select "Properties" and then "Settings". Uncheck the "Auto insert notification" checkbox.
• Try moving the CD-ROM drive to a different IDE channel, if possible. This may cause the problem to go away

Explanation: You can hear the hard disk head moving or other sounds of activity, but the system is idle and the hard disk activity LED does not light up.

Diagnosis: The most usual cause of this observed behavior is internal thermal recalibration being performed by the hard disk. This procedure is performed by many types of hard disks as they warm up, to ensure that they compensate for thermal expansion of the platters. Another feature that can cause this is the "wear leveling" feature now being used by Western Digital and possibly some other manufacturers, which causes the disk to move from track to track every 15 seconds when idle. If you see disk activity while the system is idle that includes the hard disk LED being lit,

Explanation: You have turned off power management, but the hard disk still spins down after a period of inactivity.

Diagnosis: Sometimes the power management isn't really turned off; it's possible that more than one BIOS setting needs to be changed and they weren't all changed. There could be a BIOS bug as well.

Recommendation:

• Go into the BIOS setup and double-check that power management really is turned off at a global level.
• If you are running Windows 95 OEM SR2, look in the Control Panel for an applet called "Power". Go into it, and uncheck the box that controls spinning down the hard disk.
• If the problem persists, it is possible that your BIOS has a bug. Contact your motherboard manufacturer for more information. There was definitely a bug in some Award BIOSes in late 1996 (a motherboard of mine had one). This sort of problem can normally be fixed with a flash BIOS upgrade, if available.
• There could be a problem related to the hard disk, such as a loose cable, or a defect with the hard disk itself; double-check the hard disk connection.
• Troubleshoot the motherboard.

Explanation: Every once in a while the drive makes a "click-click-click" or a clunking noise, either while it is operating or sitting idle.

Diagnosis: This is usually a message, and the message is: "look out!" Generally speaking, hard disks should not make these sorts of noises. Do not confuse a loud clicking or thunking sound with the quiet "tapping" access sound made by some drives performing thermal recalibration. Also, some newer drives (such as those made by Western Digital) use a feature called "wear leveling", that causes the disk to move from track to track every 15 seconds or so to prevent the heads from sitting over one area of the disk for an excessive period of time (which could increase the possibility of a wearout failure). Time the interval between clicks; if it is 15 seconds exactly and the drive is otherwise fine, this is likely what is going on, and you probably do not have to do anything.

Recommendation:

• Treat the disk as if it may fail at any time. This means the contents should be backed up, and no new data should be added to the drive unless it is also stored elsewhere. Keep a careful eye on the drive.
• Contact the manufacturer's technical support department. You may be told not to worry about this symptom. I suppose its possible that some hard disks are supposed to make these sorts of noises, but I won't use any that do. (Note that some drives do make an audible "clunk" but only when the PC is booting up). If the drive is new or under warranty, you may be able to get a replacement.

Explanation: The hard disk is making a buzzing or rattling noise and/or is vibrating a great deal when in operation.

Diagnosis: The most common cause of this problem is that the bearings in the drive are causing trouble. This is a relatively common problem. Noisy bearings don't affect the performance of the drive (other than aesthetically), but problems of this sort have a tendency to get worse over time. On a newer drive this is often the sign of a manufacturing defect.

Recommendation:

• Make sure that the hard disk is mounted properly into the case, as a loose drive can accentuate vibration and noise.
• Monitor the noise, if possible, over a period of several weeks. See if the noise is getting louder or not.
• Contact your manufacturer's technical support department for ideas regarding this problem and ask them to what degree noise coming from the drive is normal. Of course, many technicians will tend by nature to say "don't worry about it" but if you present yourself as persistent, polite and informed you can usually get a straight answer in most cases. If the drive is new and is making a lot of noise, in my opinion you should get it replaced.

Explanation: While performing routine file system scans, errors are being detected on one or more disk volumes. These errors are usually lost clusters or cross-linked files. Compression errors on compressed volumes are discussed here. The disk itself otherwise works OK although a handful of files might be corrupted; if the disk is corrupted to the point of unusability, or if its contents appear scrambled, look here instead.

Diagnosis: A small number of file system problems is normal on just about every PC, depending on what kind of operating system and software you are using. In particular, lost clusters are common because any time an application crashes or there is a power outage, in fact any time an application is interrupted, it may leave behind partial files that show up as lost clusters because the file was never completed properly. However, finding large quantities of lost clusters even when scanning regularly, or repeatedly finding problems like cross-linked files or invalid files or directories, can be a signal of a more serious problem.

Note: A lost cluster is not the same thing at all as a bad sector (which is a physical disk problem, not a file system problem); see here for more on those.

Recommendation: You may want to try all of the following items:

• Make sure you thoroughly scan your disk for viruses, using an up-to-date virus scanner. Corrupting the file system is a popular game with viruses.
• Make sure that you are using the correct type of disk utilities. Using a disk utility not designed for Windows 95 on a Windows 95 system, or using one not aware of FAT32 on a FAT32 volume, will cause the program to detect "errors" that don't really exist. They just don't properly understand what they are looking at because they are out of date.
• If the problem recently occurred after installing a particular piece of software, it may be that program causing the corruption. Some applications can be buggy, and especially if they crash a lot, they may leave partial files and other file system anomalies lying around. Try not using the suspect application for a few days if possible, and see if the problems go away.
• Make sure that you employ proper shutdown habits. No PC running any version of Windows should be shut down without following a proper shut down procedure.
• If you are using Windows 3.x, look for old stray .TMP files in the temporary file directory (which is often specified with a "SET TEMP=<directory>" command in your AUTOEXEC.BAT file) and delete them. These files cause system problems sometimes if allowed to accumulate.
• Check for resource conflicts. These can cause files to be corrupted.
• You may have an instability problems with your operating system installation. Look in this section for more; you may want to try reinstalling the operating system. A recently-changed driver may be the problem.
• If you have recently installed bus mastering IDE drivers, these could be causing the problem. See here for more and try uninstalling them if possible.
• You may have a real problem with the disk that is causing the difficulty. In my experience it isn't too typical to find repeated file system problems without a real disk problem manifesting itself in other ways but it is possible. Troubleshoot the disk here.

Explanation: One or more files or directories seem to have "disappeared" from a disk volume. You were using them or referenced them recently, but now they are nowhere to be found.

Diagnosis: Files that seem to be lost on a hard disk are more often simply "misplaced" than actually lost. By this I mean that the files have been moved by the user, or the wrong file name or directory name is being used, so the file is still there but seems to be gone. Rarely, a disk corruption problem or virus can really make a file disappear.

Recommendation:

• Make sure that you are really referring to the file by its correct name. I'm sorry if this sounds insulting to your intelligence, but a large percentage of problems I run into with files that seem to disappear turn out to simply be that the wrong drive letter was being used, or someone moved the file to another directory and forgot about it. You can use the "Find Files or Folders" utility built into Windows 95 to search for files by file name.
• If the file is on a removable media source, such as a floppy disk or Zip disk, make sure that the disk is still in the drive.
• Scan the system for viruses. Some viruses play tricks with the directory structure or delete files when they are activated.
• Scan the hard disk for file system corruption. File system problems can cause files to either be lost or to appear to be lost.

Explanation: The hard disk is generating error messages or is otherwise behaving as if it has become seriously corrupted. An existing, working hard disk may be acting as if it had been wiped clean, or had been never formatted. Strange error messages or very large quantities of files may be corrupted or wiped out. Note that small numbers of lost clusters or other minor file system corruption are often a result of more benign situations and are discussed here instead. (Bear in mind that if you don't scan for file systems regularly, they can accumulate and make the situation look a lot more dire than it really would be if the disk had been maintained properly.)

Diagnosis: There are a myriad of possible causes for a hard disk that is experiencing a large amount of corruption; most of them are, unfortunately, pretty serious. In many cases it is not the hard disk itself but rather an external factor that is causing the problem.

Recommendation:

• Make sure you thoroughly scan the system for viruses, using an up-to-date virus scanner. Many viruses take hard action against the file system. It is a relatively simple thing for a virus to change the disk's major structures so that it appears empty or invalid.
• Make sure that you are using the correct type of disk utilities. Using a disk utility not designed for Windows 95 on a Windows 95 system, or using one not aware of FAT32 on a FAT32 volume, can cause large amounts of corruption on a disk that is otherwise functioning properly.
• If you have just installed the disk or made changes to the inside of the system, try this troubleshooting section that focuses on common installation problems.
• If you have just moved a hard disk from an existing system where it used to work, the problem may be related to a change in how the BIOS references the disk. See here for more on this issue.
• Check for resource conflicts. These can cause problems with the hard disk.
• Check to make sure the hard disk has been set up correctly in the BIOS.
• Try disabling the enhanced performance settings in the system BIOS, and dropping down to a lower PIO mode as well. Some of the settings that don't always work in all machines include Block Mode and 32-bit access.
• Make sure that the IDE cable is not too long. Try swapping the cable or using a shorter one.
• You may have a real problem with the disk that is causing the difficulty. In my experience it isn't too typical to find repeated file system problems without a real disk problem manifesting itself in other ways but it is possible. Troubleshoot the disk here.

Explanation: You suspect, for whatever reason, a virus infection on your hard disk and are not sure what to do about it.

Diagnosis: Viruses are commonly responsible for a number of system problems that are blamed on hardware failures or software bugs. It makes sense to eliminate them as a possible problem source before ripping the machine open. Checking for viruses is normally as simple as installing a virus scanner and running it.

Recommendation: You will want to do all of the following:

• If you suspect a virus infection, stop using your PC immediately. Locate all floppy disks that have been used recently and stop using them as well. Make sure that no PCs networked to you are accessing your hard disk, or they could get whatever you have (depending on what it is).
• Read this section of the System Care Guide, which discusses viruses in detail, including what they are, how to avoid infection and what to do if you become infected. If you want the shorter version, this section  discusses virus detection and removal specifically.
• Obtain virus scanning software and follow its directions. You will normally be instructed to boot the system from a provided bootable floppy disk and scan the hard disk for viruses. You should then install the software to your hard disk and use it to scan for viruses regularly.
• Make sure you scan any floppy disks that you have used in the system for viruses as well or you may reinfect the PC again.

Explanation: You have accidentally deleted one or more files and wish to undo the deletion and recover the file.

Diagnosis: On a modern system undeleting files is relatively simple, as long as you realize relatively quickly that you want to restore the file. Regular deletion of a file doesn't actually erase the contents of the file; it simply marks the file as deleted in the directory. The file's contents remain where they were, though they are made available for other files to use. As long as you remember to try to undelete the file soon, you should be able to recover it. In addition, many operating systems and utility programs store recently-deleted files intact in case they are needed. In Windows 95, for example, this is the "Recycle Bin".

Recommendation: As soon as you realize that you want to undelete a file that you recently deleted, avoid doing anything more on the system that involves the hard disk. Every time you create or change a file, you increase the chance that the contents of the file you want to recover will be overwritten with something new, unless it is in a protected area like the Recycle Bin:

• Under Windows 95, check the Recycle Bin to see if the file you are looking for is there. If it is, this means that Windows 95 still has the file stored and you can recover it by right-clicking on it and selecting "Restore".
• If you have Norton Utilities installed, and Norton's protection installed, then it may have the file saved somewhere if Windows 95 doesn't. Other protection utilities work in a similar manner.
• Run a file recovery utility like Norton's Unerase or the DOS Undelete command. These will search for recently-deleted files in the directory and offer to undelete them. Depending on how long it has been since the file was deleted, you may have good or only partial success undeleting.
• Don't forget that if you have a current backup of your hard disk, you can use that to restore the file (at least, the file as it appeared at the time of your last backup).

Explanation: A hard disk volume has been accidentally formatted, and it is desired to get the information on the disk back again.

Diagnosis: Performing a high-level format on a hard disk doesn't really "format" it the way a low-level format does; it just writes the file system structures. As a result, reformatting a drive just wipes out the existing structures (the root directory entries, etc.). The data itself is still on the drive, unless you specifically used a special application that wipes all the data in the files as well (these programs are used sometimes for security reasons). There are unformatting utilities that will reverse the formatting process, perhaps only partially depending on the circumstances.

Recommendation:

• In order to maximize the chances of unformatting the disk, stop using it immediately. Turn off the system (safely) if possible.
• Obtain an unformatting utility and run it, following its directions. For example, there is one included as part of the Norton Utilities.

Explanation: You are using long file names in Windows 95 (file names that are longer than the standard DOS 8.3 convention) but sometimes the file's longer name disappears. For example, a file named "March Results.doc" may at some point end up having only the name "MARCHR~1.DOC". You may find that only the short file name alias shows up when you copy the file to another machine or to a floppy disk.

Diagnosis: Long file names are a welcome addition in Windows 95, but to be blunt, their implementation was a hack. In order to maintain compatibility many compromises were made in the way that they work, and several different things can cause them to become lost from the file system.

Recommendation: The problem could be caused by any combination of the following:

• Using any disk utilities that perform activities such as scanning for file system corruption, defragmentation, directory sorting and the like that are from before Windows 95 or are not long-file-name-aware, can cause the long names to be stripped from directories or even entire disks. Don't use them! Only use utilities certified to work with Windows 95.
• Older Windows and DOS applications that don't understand long file names will only see the short file name alias. Even if they are running in Windows 95, when you go to open your file with this software you will only see the short form alias, and that is all they will use when you do a "Save As" to save the file as well.
• Be wary of file transfer and backup utilities that don't handle long file names carefully. If you use older DOS software to back up your hard disk then the long names will be totally lost if/when you have to restore after a crash. If you use a DOS (older DOS, not the DOS that comes with Windows 95) file-transfer utility then the files on the destination machine will only have the short names.
• Be wary of copying files around the disk using older software. They may accidentally wipe out files that have different long names but the same short file name alias.

Explanation: You benchmarked your hard disk's performance when it was relatively new and then again recently, and noticed that the scores are going down; or, you've just noticed yourself that the disk seems to perform more slowly than it once did.

Diagnosis: This is fairly normal and is not usually indicative of a problem situation. There are several reasons why performance will tend to decrease over time. First is that when a hard disk is first used, it fills up from the outside of the disk in towards the middle. The outer part of the disk has the fastest transfer rate because of how data is recorded on the disk using zoned bit recording. Second is the tendency for files and directories to become fragmented, which hurts performance; regular defragmentation can help with this. Third, most people (if you are anything like me) enjoy collecting "neat" utilities, software enhancements, hardware drivers (for new gadgets) and install all this stuff on their machine. This will tend to slow the machine down by taking CPU cycles and also by using up memory, which can affect benchmarks and also make the PC seem generally sluggish. Finally, the system as a whole will slow down if the disk gets too full. Running with your disks more than 90% full is not ideal.

Recommendation: There isn't much you can do to prevent slowdown of this sort from happening, but there are some specific steps you can take to improve performance of your hard disk if this is an important issue to you. Also check out these tips in the System Optimization Guide:

• Don't take hard disk benchmarks too seriously. A decrease of 5% in a disk benchmark is likely to have very little impact on the real-world performance of the drive for 99% of people.
• Defragment your hard disk frequently. Allowing the file system to become fragment unnecessarily drags down performance.
• Clean out unnecessary software from your machine. Look in the StartUp folder under "Programs" in Windows 95 and remove some of the programs that are always started automatically when you boot up the machine, if you are not using them.
• If you have recently installed any new drivers, they may be affecting performance as well, though this is less likely.
• Consider partitioning your hard disk to take advantage of the fact that the outside of the disk has the highest performance. For example, you may want to partition a second 1 GB hard disk into two parts, and put the files requiring faster access in the first partition, and the rest in the second one. The first partition will be on the outside of the disk and will generally have better performance (although the difference may not be huge in the real world)

Explanation: In an attempt to improve performance on your system under Windows 95, you have installed bus mastering drivers. While the drivers work, there is no great performance improvement, as you may have been expecting.

Diagnosis: Join the club. As I've said elsewhere on this site, I find all the hoo-hah about bus mastering drivers totally amazing. Why they are so hyped up, considering that they have so many compatibility and installation problems and they provide so little real benefit for the average person, is totally beyond me. Oh well.

Recommendation:

• Don't worry about it. No performance improvement is quite common for many people running these drivers under Windows 95.
• Changing the version of bus mastering drivers installed on your system may improve the performance in some cases. Make sure you are using a version designed for your particular chipset/motherboard. Consult the motherboard manufacturer's home page for more ideas.
• Uninstall the drivers, especially if performance is decreasing or there are compatibility issues.

Explanation: You upgraded or replaced your hard disk, but it is still performing at a speed comparable to your older drive. The transfer rate performance is not quite as good as you were expecting, or benchmarks are lower than what others are getting for the drive.

Diagnosis: As discussed in detail in this Reference Guide section on hard disk performance, the performance level of a hard disk is dependent on many different factors. Some of these are a function of the hard disk itself, but many are a function of the other parts of the system. Most hard disk benchmarks in fact are influenced by the speed of the chipset, processor, memory and other components. Also, putting a new hard disk into an old motherboard can greatly limit its performance because the interface may not be capable of running at the higher modes that are required for peak performance. Remember to check out this section in the Optimization Guide on hard disk performance.

Recommendation:

• Be careful about how you interpret benchmarks. In a nutshell, many benchmarks are deceiving and may give you an incorrect picture of how your hardware is really working.
• Running a new hard disk on a system that uses ISA-based hard disk I/O will severely limit performance. I would strongly recommend a motherboard upgrade for any system that does not have at least a VESA local bus hard disk controller.
• Many older systems do not support the faster PIO modes required for high-speed transfers to and from modern hard disks. In particular, if your system uses a 486 class motherboard and an expansion-slot hard disk controller, it may only support the slower PIO modes. In this case, the peak transfer rate of the hard disk will be reduced. You may want to upgrade to a newer controller or motherboard.
• Some motherboards support higher PIO modes on their primary IDE channel than they do on their secondary channel. If the new drive is on the secondary channel you may see a speed increase by moving it to the primary. Consult your motherboard documentation.
• Motherboards that do not support independent drive timing will slow down a faster disk if it is shared master/slave on a channel with an older disk. You may want to try the disk on a separate channel.
• Make sure that the new hard disk is properly set up in the BIOS. Some systems may not set the disk to the optimum performance settings automatically, even when they autodetect a drive. You want to make sure that the PIO mode is set to the correct value, and also that block mode and 32-bit transfers are enabled (if the drive supports them and if they don't create any problems.)
• Hard disks will generally just perform slowly on an older system overall. The hard disk's transfers are affected a great deal by the speed of the CPU and the motherboard, and a new, fast 2 GB drive is going to run much more slowly on a 486DX2-66 than it is on a Pentium 200, all else being equal.

Explanation: Windows 95 OEM SR2 is installed, which allows the use of FAT32 partitions, but after installing it, the system still appears to be using the older FAT (FAT16) disk volumes.

Diagnosis: FAT32 is a disk format, and while support for it is part of Windows 95 OEM SR2, this does not mean your disk volumes automatically are always going to be FAT32 just because you are running OSR2. You must use the correct tools and create FAT32 volumes if you want to use them, or convert your existing FAT16 volumes to FAT32.

Recommendation:

• Make sure that you really do have OEM SR2 installed. See this procedure for instructions on checking the Windows 95 version.
• See this section on the tradeoffs in using FAT32.
• When running Windows 95 OEM SR2, make sure you use the correct version of FDISK, the one that came with the operating system. Any older versions do not know about FAT32 at all.
• If you have upgraded an existing system then you will need to either repartition the existing disk volumes using FDISK to make them FAT32, or convert them. Partition Magic is a utility that will do this conversion for you; conversion is not supported natively in Windows 95 because OEM SR2 was designed only to be installed on new PCs (thus the name "OEM").
• Remember that the FDISK program that supports FAT32 only enables the support for partitions that are greater than 512 MB in size. If you run FDISK in a system that has only hard disks under 512 MB in size, they will not be formatted using FAT32. There is no practical need to use FAT32 for drives this small

Explanation: In an attempt to improve performance on your system under Windows 95, you have installed PCI bus mastering IDE drivers. After installation, problems are being exhibited ranging from hard disks not working correctly or being recognized, CD-ROM drives not working, general system instability, or other issues.

Diagnosis: In my opinion, setting up bus mastering IDE under Windows 95 has the lowest value (measured as the ratio of true performance improvement to implementation hassle and cost) of just about anything you can do to optimize your machine. There are so many different problems that they cause, and so many pieces of hardware and software they don't work with, that I no longer bother with them due to the minuscule improvements I see when using them. In short, if the problem appears after installing these drivers, I generally recommend uninstalling and forgetting about them. Below I list some specific gotchas and incompatibilites to watch out for. When you see how long it is (and I am sure that it is not comprehensive) you will know why I don't bother with these drivers any more.

Recommendation: First of all, read this section in the Reference Guide that discusses the requirements for running PCI IDE bus mastering. Then also read this section on IDE bus mastering in general. Then, consult the list below for possible specific causes of your problems; you may find something here that will help you fix the trouble, but it is just as likely that you will simply find confirmation that they just are not going to work with your PC:

• Make sure that your hard disk is working properly before you attempt to install these drivers. This ensures making sure that it is virus-free and stable. Make sure the operating system and the PC as a whole are working well before you start, or you may end up with a confusing mess of symptoms, some of which may be driver-related and some not.
• Bus mastering drivers are simply not compatible with many types of hard disks (especially older ones) and ATAPI devices such as CD-ROM drives. Check the "read me" file that comes with the bus mastering drivers and see if yours is listed.
• These drivers will often not support non-CD-ROM ATAPI devices such as tape drives, IDE Zip drives, etc.
• Bus mastering drivers generally do not work with hard disks using dynamic drive overlays to allow access to hard disks larger than 504 MB (these should not be necessary on most motherboards that will work with these drivers anyway).
• Some drivers are not compatible with some motherboards, period.
• Sometimes a newer release of these drivers will not work while an older one does. You may want to try restoring to the older set of drivers. Check your motherboard manufacturer's home page for possibly more information.
• Look for a set of bus mastering drivers specific to your motherboard. These are often found at the motherboard manufacturer's home page. They may work better than the generic Intel drivers, under some circumstances.
• Some CD-ROM drives will not work with these drivers installed if they are the only drives on either the primary or secondary IDE channels. They may have to be configured as a slave to a hard disk.
• The bus mastering drivers will generally not work if there is an add-on IDE controller installed on the system. If you have a sound card for example with an IDE interface, you will need to disable it or remove the bus mastering drivers. If you have a third-party add-in IDE controller, it may not work.
• You may need to remove any special device drivers designed for controlling IDE hard disks or ATAPI CD-ROM drives that are loaded in your CONFIG.SYS file. Note that this will make it impossible for you to use your CD-ROM drive after doing a "Restart the computer in MS-DOS mode". You will have to reboot the PC into a custom configuration and then reboot again (which is a pain in the butt). See here for more details.
• The drivers may not function if the IDE cables used are too long. If the cables are near the maximum allowable length (18 inches) then try shortening them.
• If you need to uninstall the bus mastering drivers, follow the instructions in the "read me" file that accompanied them. An uninstall facility may be included. However, in some cases you will be forced to reinstall Windows 95 to rid yourself of these drivers (another reason why I don't like them).

Explanation: In an attempt to improve performance on your system under Windows 95, you have installed bus mastering drivers. While the drivers work, there is no great performance improvement, as you may have been expecting.

Diagnosis: Join the club. As I've said elsewhere on this site, I find all the hoo-hah about bus mastering drivers totally amazing. Why they are so hyped up, considering that they have so many compatibility and installation problems and they provide so little real benefit for the average person, is totally beyond me. Oh well.

Recommendation:

• Don't worry about it. No performance improvement is quite common for many people running these drivers under Windows 95.
• Changing the version of bus mastering drivers installed on your system may improve the performance in some cases. Make sure you are using a version designed for your particular chipset/motherboard. Consult the motherboard manufacturer's home page for more ideas.
• Uninstall the drivers, especially if performance is decreasing or there are compatibility issues.

Explanation: There is an option in Windows 3.x to enable so-called "32-bit disk access" but whenever you enable it, an error message is generated saying that a problem occurred and you have to turn it off.

Diagnosis: First of all, this feature was totally misnamed by Microsoft. There is no such thing as "32-bit access" to an IDE hard disk, because the IDE/ATA interface is 16 bits wide. The 32 bits being talked about here really refer to the use of 32-bit protected-mode software to access the hard disk. In essence, its simply about using better drivers to access the disk instead of using the native BIOS disk routines. The problem is that Windows 3.x ships only with an ancient generic driver that is five years old and does not handle modern hard disks properly. Unless you are using an older hard disk, you need a specific driver to handle your disk to enable this feature.

Recommendation:

• Look at your hard disk manufacturer's technical support web page, where you will most likely find a driver that is designed specifically to allow that manufacturer's disks to work with Windows 3.x 32-bit disk access. I am not sure what you are supposed to do if you have multiple disks from different vendors running on your system, however...
• Just disable 32-bit disk access, and don't worry about it. While it does improve disk performance, the difference is not enormous and if it doesn't work properly, it's not something you need to worry about a great deal in my opinion.

Explanation: The system seems to be going to the hard disk a lot, even when you are working only with items that are already in memory. For example, when scrolling up and down in a large file, there may be a pause while the hard disk is activated. You may especially notice it when swapping between applications.

Diagnosis: The most usual cause of this sort of behavior is what is called thrashing. This refers to the excessive use of virtual memory paging to compensate for having insufficient real physical memory to hold all of the applications and data that are in use. Especially if you are using many applications or large files, and also if there isn't a great deal of real memory in the PC, the operating system will have to move some of the contents of memory to the hard disk when it runs out of space. Then, when you need whatever was swapped to disk, it is loaded and something else is swapped to the disk. This is a supply and demand situation; the only way to resolve it is to increase the supply of real memory, or reduce the demand created by applications and data open simultaneously.

Recommendation:

• Read this section on virtual memory and this section on choosing a sensible memory size for the operating system and application you are using.
• If you can afford to do so, upgrade the amount of physical memory in the system, especially if you don't have enough memory in the PC for optimal performance based on your operating system. Memory is cheap today and it provides great performance improvement in many cases.
• Consult this section of the Optimization Guide for suggestions on optimizing the virtual memory setup of your system. These simple steps can greatly improve performance at no cost.
• Reduce the number of applications running in the system, and reduce the number of data files you have open. If you are finished using something, close it to free up memory for programs you are still using.
• Cut down on the number of "toys" that load automatically when the system starts up. The more automatic utilities, scheduling reminder programs, memory-resident tools and other gadgets that load when the system starts up, the less memory that is available for "real" applications, and the more likely that thrashing will occur.