Maybe someone can help me out here.

So today I shut down my brothers computer with the P35C-DS3R and then later I tried powering it back on, and it doesn't boot. No lights, no fans, nothing is turned on period. So to make sure it wasn't my power supply, I did the jumper trick and the power supply turns on fine (fan spins, fans connected to it turned on, etc.) So now I'm wondering if it is the motherboard that died. Is there a good procedure to test out if the motherboard is dead and not some other component?