My computer will sometimes power down with power still going to the motherboard with apparent lights still emanating from it. When i try to start it up after this happens it will turn on for maybe half a second then instantly quit, I usually have to wait about 10 minutes before I can turn the computer back on. I built this system myself two years ago and had the same problem? I think it could be the graphics card? its a 9800 gtx. My powersupply is 700w im running an Intel core duo e8500 @ 3.16Ghz (2 cpus) ~3.2Ghz. with 4 gigs of ram. The motherboard is an xfx nForce 780i. And of course vista ultimate 64 is my operating system. Thanks!