Blown A7N8X-LA?

I was lookin at a buddys computer cuz he was having video issues. Ended up being a blow video card...took it out...the on board video worked. I had the genius idea to upgrade his power supply cuz he was running a stock HP 250 watter. After doing this whenever I connect power to the supply, the power light on the box turns on, no fans or beeps. Pressing the power switch does nothing. I have tried to replace the power supply with the original and another, but still no luck. I reseated the power switch and reset the cmos, but I just am at a loss here. Am I going to have to buy him a new motherboard?