Leave the cover off.
i just recently bought an evga 7800gs. i'm somewhat having a problem with it that i can't figure out for the life of me. after about 10 minutes or so after the card is setup and everything, my pc tends to shut down or reboot itself. i've tried rolling back the drivers, but it still does the same thing. i don't think anything is wrong with the card itself. i have a feeling it's my psu, but i'd like some feedback.
here are my computer specs(if you need more detail, i'll be happy to post):
pentium d 3.00ghz
atx 500w psu