Does the motherboard have to have a certian power supply? I mean the cord fits into the motherboard, but does it need something beyond that? I just got a new mb and Im useing my old box and it starts up, then dies in bout 5 sec. I tryed pluging my old mb into my brothers even older power and something similar happed. My ps is only 250w, and the book suggests a 350 for a heavy system, but I didnt have anything pluged in at the time. Does this mean I need a new power supply?