Did you upgrade to Windows XP? If you are getting a Blue screen, you are having hardware issues. But it sounds like you need to reinstall the operating system that will fix most if not all your problems.
If this is a fresh install of windows it is doubtful a reinstall will fix the issue. Did you install ANY aplications or hardware after installing XP? If so, tell us what they were. Check your device manager and see if you have any exclamations or question marks. After installing XP did you install the necessary motherboard drivers? If you log into safe mode does the same thing happen?
Carlosdl is right. It sounds like the processor is overheating. After a fresh install you don’t have to worry about drivers, XP will be stable before loading any drivers, and bad drivers will cause blue screens.