Computer keeps rebooting itself. I assumed this was a overheating issue. Computer will run fine for a few hours and then automatically reboot. Sometimes it happens after 10 minutes, other times after an hour. Very strange.

Took off the cover, cleaned out all the dust (suprised how much there was) with compressed air. Cover is still off, and even have an external fan blowing on it.

Running XP. Speedfan clocks everything at a good temp except for the GPU which is at around 58-60 degrees

Ran malware bytes, adware and spybot. Found a few minor things but cleaned them out. Im stumped as to why this is going on.

All help is appreciated.

Thanks

It is easier to troubleshoot whether it is a Windows/software/driver problem or a hardware problem if testing is done outside Windows.

All fans running?

How stable is the utility power?

How old is it?
3+ years suspect flaky power supply. 1+ years for low quality supply.

If this is a new or re-build, was thermal paste between processor and heat sink applied properly?

Processor overheating?
Usually results in one or more of these behaviors depending on age of processor:

Reduced performance - Clock throttling/no-ops to avoid overheating.
Reboots/lockups
Damaged processor

Remove drives, adapter cards, and peripherals to isolate and try to force the issue with just the processor, memory, and motherboard. Stress test utilities such as one of the Memtest variants or Prime95 can be helpful.