I just installed a nvidia gtx 660 in my computer. It ran well for about a half hour I was watching the temp and it never went above 59c. Then it randomly shut off midgame but I was able to restart. I turned the fan % up to 25 (thinking it may have been overheating) and started playing a game and mid game it completely shut down and now it will not turn back on. I tried to reinstall the old graphics card and it still did not start. I believe everything is getting power because the light on my graphics card is still light up green but the computer will not boot up at all.