When you press the power button, it sounds like it wants to start up, but then goes dead. And it is a good 15 minutes later before it will start up. There are 3 fans in the computer and I even leave the side open when I use it. I have a heat monitor on it and it never goes above the shut off point. Also, when I was doing the stress test on the video card, thats when it shut down, not when I was doing other stress tests on other parts. The stress test on the motherboard was fine too. I have always been able to change out drives and such on my computer but never a motherboard or video card or power supply. Are these difficult and should I do one thing at a time? I took my computer to a professional and of course, he didn't find anything wrong with it. It never did shut down on him! I have always thought this was either a heat problem or a bad video card. Thanks