Remove all the hard disks, and all the cards except the video card of choice. If you have multiple memory modules, only use one to start. See if you can get this configuration working, swapping memory and/or video cards until you're either successful or you run out of spares. If you try several video cards, and several memory modules, and still can't get anywhere, you've pretty much narrowed it down to the MB or P/S. Next step it to swap out the P/S I would imagine...