O.K., is it my motherboard
I've been involved in the computer field for over 40 years now, but only been into PCs for about 10 and do not profess to be a computer guru or technical guy. But, I have had a recent problem that I paid a guy ($85) who was supposed to be a technical guy to solve. He told me I had a bad HD and installed a full version of Windows XP Home. I had only been using an Upgrade version previously which seem to have little or no bearing on my problem. I might add that the 'bad HD' is still in use in another system. The problem in reality was that the power supply fan within the case was gonzo, thus likely resulting in overheating within the case. Being located very, very close to the CPU it apparently was causing failures that seemed like possible shorts in the motherboard. I would assume a bad HD would result in a message regarding, perhaps, an 'invalid boot device' rather than a shut down. The number of computers, the attendant components, attached devices, software, etc. make such a tremendously varied world that it gets really crazy to try to debug some issues. Even if you have had the same problem, the answer for someone else might not be the same nor work. It's a very interesting world - hang in there and good luck with your problem!! Note that on the system with the supposedly bad HD that I had two HDs in the case and he installed on the 2nd.