Thanks for your advice toxic, after reading your post I tried it with a different power supply that I know works, and unfortunately I still get the same problem... I think snake-eyes is right, it has to be a problem with the cpu. The cpu is either damaged somehow, or simply overheating. When I get a chance I will go buy some thermal compound and try that, I'm not exactly making it my highest priority because I am not making any money for this, I am simply building this computer as a favor for an in-law, and she is actually really ****ing me off and clearly doesn't appreciate it at all, so helping her was a big mistake on my part - I was just trying to save her spending hundreds of dollars on a new computer... whatever... anyway, thanks to everyone who gave me advice, I really appreciate it. Hopefully the thermal compound will work, because I can't afford a new cpu. By the way, in response to your question, I took a closer look at the motherboard and it is an msi 845 pro v1. Thanks again, everyone.