I have two fans in my system. One on the case, one on the CPU. I have drilled ventalation holes near the HD and power supply and never had any heat problems. In fact, I could probably lose the CPU fan (it isn't spinning very well anyway) and just use the main fan as it is right above the CPU. See the link on "Player" in my sig for pictures. For what it's worth, this has run through very hot summers, for hours on end, in the sunlight, with the car turned off and all windows up. I don't have an air conditioner.