One of the most important elements of PC security is disk or hard drive security. Your hard drive stores all your data, your internet history, your credit card and bank account numbers. emails and addresses. It has to in order to work conveniently and efficiently for you. But there's a down side to this convenient efficiency. Unless you are careful, that info/data can be seen or recovered by someone other than yourself. However, there are a number of ways to prevent this from happening. The best way, the obvious way, is to not store any valuable personal data on your PC at all. However, that is impractical for many of us. So we have to find a compromise between airtight security and carelessness. One is to password protect your personal data and/or store it in a firewall "safe". If you share your PC with someone else, make sure your logon account is password enabled and that you keep your password a secret. Another method of privacy protection is secure deletion of your sensitive data. Not many people realize this, but when you right click on an item in Windows and select Delete, you have really haven't deleted it at all. In fact, all you've done is remove the file header from the OS (operating system) directory. That data can be recovered by someone with the right hardware or software. It's like being listed in an office building directory and having your name/business removed from the directory without moving your office out of the building. Anybody walking by your office or asking about you will still be able to find you. What you really want is to remove all trace of your presecnce in the building for good. This requires overwriting or "shredding" the data with random numbers and characters at least seven to ten times (in my opinion). Overwriting is the only way to secure data from prying eyes.It can not be removed from the disk physically. Think of writing a bad word about your teacher on the chalkboard. You've done it, had a laugh, but now you want to make sure the teacher doesn't find out about it. But there's one problem: you don't have a chalkbrush. So all you can do is to scribble over the "incriminating" words until they can no longer be seen. That's called "overwriting".
There are many overwriting methods. The best methods are the ones that overwrite the data many times writing 1s and 0s (typically) to the drive. It's a simple equation, the more you overwrite the data, the less chance someone will have of recovering it.
The good news is you don't have to do the overwriting. There are a number of utilities that will do this for you. A couple of them are free. One is Eraser the other is Cleanup. Both these tools are similar to CCleaner but go CCleaner one better. They not only delete your internet history and personal data but "shred" it as well. The only problem with these free utilities as I have said elsewhere is that you don't get product support from the people who made them. You have to rely on forums and FAQ's to take care of problems you might have using them.
Unless you're technically inclined, it's probably best to go with a payware data shredder. The ones I have used and think are good enough to recommend them to you are CyberScrub, Anti Tracks,Tracks Eraser Pro and Acronis Privacy Expert Suite which is quite simple to use. Each of these tools allow you to choose the method of overwrite. Some, like CyberScrub, allow you to change and edit the overwrite methods. Most of these programs are pretty self explanatory but it's a really good idea to look at the Help file in each of these utilities just the same.
There are many data shredding utilities on the market so shop around and download their trial versions to make sure you can use them and that they will not harm your system.
If you are going to give your PC away or turn it over to someone, you will need a disk sanitizer, one that erases all the data on your drive.
Again, there are many of these programs out there. If you buy them online you have to burn them to a CD or floppy disk. You can also order them directly from the company and they will arrive in CD or floppy form ready to go. To use them, all you have to do is insert the disk, turn you PC off, restart it, make sure to boot off the disk you just inserted and follow the directions on your screen form there. Some products in this area to consider are cyberCide,Acronis Drive Cleanser and Wipe Drive
A couple of things to keep in mind when using these utilities:
One, the jury is still out as to whether just a few or many overwrites is required for data security. Peter Gutmann, a pioneer and authority in this area, advocates a 35 pass overwrite. Some in the field think this is overkill. A number of really good papers and articles have, in addition to Gutmann's, have been written on the subject of secure deletion. If I were you I would go with a minimum of seven to ten overwrite method.
Two, proper shredding takes a long time unless you have a very small drive. If you want to secure an 80 GB drive with a seven pass overwrite method you should set aside a couple of days. It will take almost a week to secure a hard drive using the Gutmann method on an 80 GB drive. If all you want to do is erase a days worth of internet history , you should expect it to take an hour or so using the Gutmann method, a half hour using the DOD method. Even using a single pass overwrite on a 40 GB drive should take no less than an hour. A lot of it depends on your Memory and CPU.
My point here is that secure deletion takes a while to do right. You have to be patient. If you are surprised at how quickly your disk wiper did its job, chances are it didn't do its job.
An alternative to overwriting your sensitive data is to encrypt your data before you store it on your disk. There are a number of good and free encryption utilities available for you to choose from, for example (Pretty Good Privacy). Here is a list of free encryption utilities. Microsoft Office comes with an encrypting capability.
Another way to "sterilize" your disk is to demagnetize it or degauss (the unit of measure of magnetic inductive force is the gauss, named for mathematician Karl Friedrich Gauss) it. Degaussing is a technology developed in the Second World War to protect British and Allied ships from German naval mines which used fuses designed to detonate the mine(s)upon detection of disturbances in the surrounding magnetic field triggered by the hull of a passing ship or submarine. Simply stated, degaussing makes data unrecoverable by neutralizing the magnetic alignment and orientation of the data stored on your disk so that when a read head is applied to the degaussed disk, the data will not respond to its magnetic pull, if you will. It's pretty hard on your drive (disk). In fact, it's about as close to destroying your disk as you can get without picking up a hammer. Usually (not always) the disk or storage media is rendered inoperable as a result of being degaussed or demagnetized.
If you want to be 101% sure that data on your drive is secure, you have to destroy the disk itself. Either burn it, smash it or crush it. (Save this for a day you need the therapy! 
) There's no other way to do it.
