** Firstly: I take no responsibility for any damages that come about through an attempt to follow these instructions. You will be using customized drivers, rather than the official ones, so make sure you know the risks**
Until recently, I had a great deal of trouble with trying to run Half Life 2 on my laptop, equipped with the Intel GMA945 integrated graphics controller. The infamous stuttering bug was taken almost to absurdity, the game shuddering to a halt at any opportunity and often crashing entirely. I tried everything: redownloading the files, updating the drivers, checking that other software or processes weren't causing a problem.
That's when I discovered MAD_BEAST's custom GMA drivers. With one simple operation, Half Life 2 was rendered playable, even with the graphics settings set to maximum. Though occassionally hit by slowdown, the Source engine and its games are now fully operational on my machine.
Here's how to install these drivers.
First, try searching for "MAD_BEAST custom drivers" (or MAD_BEAST hacked drivers), or check the Intel 9XX gaming Google Group. Download it, and try to use the installer.
If the installer doesn't work, or the installer insists that your machine doesn't meet the hardware requirements (as it did mine, as technically the driver is not built for the 945, but rather the 950 and above), you can (though be sure you know what you're doing!) use the device manager to manually select a new driver for the GMA, and select the inf files that came with the download - usually igfxp32.inf will be the one that you want.
Be sure that you know how to start in safe mode, just in case things go wrong.
Select the driver, and choose it, ignoring Window's whine that it isn't digitally signed.