I have here a computer that was built for me around last year. There have been a few problems with it over the year, which were seemingly fixed. I just ordered and received a new graphics card (Radeon x800) since it seemed to me that my old graphics card had been physically damaged as it displayed incorrectly on my monitor.
I installed the new card and turned the machine on just fine. Went through everything fine... now the second or third time turning the machine on, it just restarts in an endless loop. Nothing appears on the screen, and I can hear the machine endlessly restarting from the sound of my CD drives. I'm assuming this is a problem with the mother board.
It's safe to assume that everything in my machine is compatible with everthing else, and that I have checked the obvious (cables connected, etc...) mostly. :P