Well, XP is now up & running.
Jeff Olsen: I’m still betting on overheating. If a fan DID fail, the system is going to overheat before it completes the boot process. Open the case, check to see if all the fans are spinning properly. While the case is open, take a flashlight and shine it on the capacitors (cylindrical things that look like batteries) on the motherboard, especially those in the vicinity of the CPU. If any of them are bulging at the top, or leaking a brownish fluid (it might have dried to a brownish crust), the motherboard needs to be replaced.
Actually, the case has been open all this time. The Athlon has been acting a little weird ever since I installed an ATI TV Wonder card and a second hard drive. For a while, I was having so many problems that it was eaiser to leave the side off and I haven’t bothered to put it back yet.
While you can do this it is best to backup all your data, reformat and re-install Windows. It will just work better but it is more work re-installing all the software that you need on your computer.