Heat is the number one killer when it comes to computer hardware. If it does not blow your CPU within a few days it sure as well lessen the lifespam by quite a bit. Not to mention that when your CPU gets toasty your computer will run like shit.
There is no point to installing tf2 if you do not have your computer setup right. I run 2 video cards a 800 watt power supply and 4 gigs of OCZ ram. The most important part of my entire setup is the cooling. If you cannot dissipate the heat that some of the hardware makes you will be done for.