I open up my older Compaq Presario computer to upgrade it with a newer but old video card (3d prophet 4500) that used to be in it. (so I know it should work with it) Anyways, I install the new card, plug it in, hit the power, nothing. Absolute silence. It works perfectly 1 minute and not at all the next. Just to be clear, there is no click, no hum of a fan, zip. I tried using a different power cord in a different outlet and I get nothing, so I know its something inside. All the cables going from the power supply are securely attached to the various bits they go to... Do I just need a new power supply or what?