My dad has recently been having a problem with his desktop computer. It first started when he said he logged into his windows name and it said "cannot display this video mode" and shut off. after this, the monitor wont display anything. i assumed he changed the setting to a value the monitor couldnt handle and he said he hadnt but i still tried a monitor with higher resolutions. none of the monitors i tried worked and I thought it was the video card. we bought a new card and everything started up and it seemed to be working. then it shut off randomly after i left it running for about 30 minutes. after this it does the same thing. computer wont display video and the power light doesnt light up anymore. I unplug the computer from the wall, take out the video card, plug it back in and start it up. it turns on and powers up. i then shut it off and put the video card back in and it displays video again. then it will shut off again after some time. Im not sure whats causing this problem and i live a good way from a best buy or any other electronics store. any help will be appreciated. thank you.