You might need to take quite a good look at your Grapics Advanced settings or your main System Advanced Settings (uno, the control panel that controls everything in the system)
Warning! BEFORE you go into the advanced system settings, backup your files to a REMOVEABLE disk, not the HD Windows is installed, not the Recovery partion, a blank CD or DVD will do, or better yet if you have another computer, and a network, you can send your backup there, also make sure to make a set of recovery discs in the event of the system failing.
PS: if you are going to use the Backup program shipped with XP Pro, make sure to use advanced mode.