PC Restarting

Have you tried a different power supply?

If it is not the motherboard, or CPU, the power supply is the next most likely suspect.

Check if the fan on the power supply is working properly, and clean out the dust.
If the power supply fan is bad,or the supply is plugged with dust, I would just replace the entire supply.

Next, I would wipe the hard drive, and do a clean install of Windows.

Chas

If it's not the CPU or motherboard (and you've done the obvious like remove all but the minimal components - system, hd, videocard - and verified the connections etc are good), I would check the power supply and the RAM. They can easily cause this type of issue.

Also, rather than just default setting your BIOS, make sure that it is configured correctly for the system. I've seen autodetection settings in the BIOS come up wrong. and cause havoc on a system. If you're using jumpers on the MB, double check them.

If this doesn't help, where does it restart? Do you get any messages? Is it repeatable (same time/software/etc?).

Give us some more details and we may be able to offer more insight.

Good luck!

if the power supply isnt putting out enough power it will restart you can check the voltage or try another power supply but if you need it-
yellow wire +12volts
red +5v
blue -12v
white -5v
purple +5v
grey +5v
orange +3.3v
brown +3.3v
green +.6v
these are for ATX and AT supply