Power comes on screen is dead
i put an nvidea geforce fx5500 256mb agp graphics card in my computer. It sometimes turns on fine and works for about an hour, but then the screen freezes, makes some pretty colours, then turns off. The computer stays on the the screen refuses to do anything. the computer will then not turn back on for a couple of hours, or it will turn on but the screen stays dead. I have tried taking the card out, but the same happens again, so it doesn't seem to be the card.