This guide is for MS Windows XP Home SP2, although it should be fine for other versions of XP (like Pro).
The guide assumes you have access to your own XP installation CD and can re-start Windows XP.

		When your computer is on, insert your Windows XP installation CD into your optical (CD/DVD) drive. I use an OEM version of XP home; your installation CD might look different from the one shown.
		In all likelihood, the "Welcome to Microsoft Windows XP" box will pop up on your desktop. If this happens, just close the box, by clicking "Exit", or the in the top right of the box.
		The next step is to go the "Start" button, click it and then select and click "Run..." as shown. I'm using Windows XP with the "Classic" Windows look; you may be using the default XP look. If you are using the default look "Run.." should still be on the start menu, so just select and click it where ever it happens to be.
		After you click "Run...", the run dialogue box should appear. When the run dialogue box appears type "sfc /scannow" without quotation marks into the space provided and then click "OK".
		After a very short period of time, the "Windows File Protection" progress box should appear and the progress bar should slowly start to move. Depending on your hardware you may have to wait for up to an hour (or possibly longer) for the process to complete. On the average computer it shouldn't take more than 30 minutes. When the process completes, the progress box will simply disappear. It is best to restart Windows after the process completes.

The "sfc /scannow" process is used to fix critical Windows files if they become corrupt. Corrupted Windows files can cause Blue Screen crashes, system freezes and unwanted system re-starts.