All of a sudden when Windows XP Professional is running it just dies and the computer tries to reboot. It always reboots fine into Windows but it happens within minutes of Windows XP running. Is this a power supply problem? A motherboard problem? A virus? Windows XP Professional is hosed? How do I go about figuring out what's wrong with this computer?
Hard to do without some additional info about your system:
Motherboard make and model:
RAM make and model:
GPU(s) make and model:
PSU make and model:
Other stuff connected to the board, make and model:
CPU fan spinning?
Other fan(s) spinning?
Lots of dust in case?
Have you tried running anti-virus and anti-spyware programs? If so, which ones? Results?
Most likely cause is going to be power supply or motherboard. I have seen this before with an older dell. If you absolutely must troubleshoot the issue, and are willing to spend some money working it, I would spend $50 on a decent power supply first. That is, unless you have access to replacement parts for free, such as borrowing from a friend or family member, then use that source first.
I was thinking along the lines of maybe someone makes a device that monitors power supply voltages and records them or shows them so that when Windows drops out and the computer tries to reboot I would know if the power supply sustained a major voltage (I don't think amperage is involved... that's just AC right?) drop. Perhaps something along the same lines of recording or showing what's happening on the motherboard to see if the problem can be isolated this way without just changing components out. This is what I meant by logic instead of being a part changing idiot... perhaps this is more of an automotive term?