CPU Keeps Restarting, Want to Break it

[Jeffage]

Ok...here's the scenario. My CPU (which I'm on right now) will just spontaneously restart for no reason. It happens randomly and with no warning...usually like once an hour. The CPU was built by a friend a couple years ago and is decently souped up. After I take off the option to have the CPU restart if there are problems, I get the BSOD. Seems like a hardware problem (video driver, etc) - I backed up all my [censored] and reinstalled windows with my friend's help. It worked for a bit and is more stable than before but is still restarting at random. So basically I can't gamble.

Is it time to junk this thing - I'm at the end of my rope and know nothing about this. Do I just start buying random crap? Motherboard, etc? My friend is on the case and knows his stuff but I need a reliable operating system. And I want to break something. Any insight?

Jeff