How to Restore Your Computer System in Windows XP
Things You'll Need
Instructions
1Click on "Start" and select "All Programs." Open the "Accessories" and move to "System Tools," then click on System Restore. The next screen is a Welcome to System Restore.
2
Select "Restore my computer to an earlier time." The next screen displays a calendar showing choices of restore points. Select your desired restore point date and click "Next."
3
Click "Next" again to confirm your choice and the computer will start restoring itself. The system restarts during the restore process.
Source...