pc reboots

windows xp sp3
asus socket 754
amd 64
2gb ram

pc reboots upon boot and reaching windows desktop.
it will reboot about 3 times before finally booting and working fine. it may run for about an hour or two before shutting itself off.


what could it be? hardware, software? im ready to buy something if i knew what to replace

First, I'd check for excess dust. Clean out everything you can find inside your PC. About $8 for a can of air

Second, check and reseat all cable and power connectors. One may be just a tad loose and causing problem before it warms up. And they can crop up again when it's quite warm causing contact problem.

Third, I'm inclined to think your PSU is failing. If cleaning dust and reseating connectors doesn't help, consider a new power supply unit.

Might be your PSU, what brand is it and how long have you had it?