Ok, I think I've narrowed it down a bit. I'm pretty sure it must be one of the main hardware components because it has even locked up while in BIOS, just changing around settings. It's not the RAM, I've replaced the chip and tried different slots. I don't think it's cooling, heat sink is warm, all fans are spinning, but nothing seems overly hot. It's neither hard-drive, because I've hooked them up independently and on both IDE channels. The only other thing I can think of, as mentioned, is power supply. How could I go about making sure that's it? Is there anyway to without buying another one just to see? Do you think it could be something loose inside and would be an easy fix, or are they pretty complicated devices?

Thanks