Okay. My win 7 computer started shutting down randomly a while back. It will start up and run for a while (10, 15 30 minutes) and then shut off abruptly with no warning. When I say shut off, I mean like you pulled the plug out of the wall. There does not seem to be a pattern to what causes it. At first I thought was the power source so I replaced that. The problem remained. Then I thought is was the graphics card, so I replaced that. Still shutting down. Now I am stumped. What can it be?