I recently had a problem with my system getting into a reboot loop. I would turn my system on, it would post fine and as soon as windows XP would start to load it would reboot again. Some times I would get to the "start window in safe mode" screen and I would try to start in safe mode. It would loop again. Now this was intermittent.

I replaced my processor, my motherboard, unplugged my ROM and Recorder and took out my GeForce video card. I was able to start up once and turned off the automatic reboot in XP and was able to see the error message "Unmountable_Boot_Volume". Called tech support. To make a long story short it was my cable. I had put an old IDE cable on. It was a 40 pin. I needed a 80 pin. Are all cables the same? NO. Use the cable that came with the motherboard or go buy a new one. It is the simplist things that make things so messed up. I hope this tip helps someone.