[RawAlex]

PCs can run pretty hot before they get too upset. The room temp only is an issue because it lowers the ability of the computer to cool itself. Depending on your system / motherboard, you may find a utility from the manufacture that would allow you to see the CPU temps and such, which can give you an idea what is going on. My quad core I am working on runs about 40C to 55C depending on work load. The one I installed for the HT system has a much larger zalman fan on the CPU, and runs at about 30C.

If you start seeing consistant temps over 60C, you are likely to start seeing blue screens or having random resets. That would be a good time to worry. Otherwise, you may just want to turn on a fan and circulate the air around the PC, remember that even 81F air is still much cooler than the PC itself.