Overheating

I offered to help fix my friend's computer, but I'm stuck. The damn thing overheats. Even when it sits idle and there's no programs open the CPU temperature is 135°F. I did a spyware and virus scan and nothing was found. The computer does not lag, it just gets ridiculously high temperatures. We dusted the case out and the overheating continued. The only other thing I can think of is that perhaps I need to reapply some thermal compound. What do you guys think?

Is the chip overclocking from your settings on the motherboard?

Are the voltages also inappropriate set from your settings on the motherboard?

Thermal compound should be checked and reapplied, as you said.

The CPU fan might not be running, or is running too slowly.

Reapply some thermal compound.

Remove residue first, obviously.

Its better if you just take the fan off and blow on the CPU when running games if they start to lag