Check it with a multimeter. Or you can "ghetto rig" test it with a paperclip and alot of HD/fans/and cd rom drives....
What you do is take a paper clip and place one end of the paperclip in the green wire port on the mobo connector, than take the other end and place it into any black wire port. It should jumpstart it. But before you turn it on make sure you have as many components hooked up as possible to see if it can handle the load. If the PSU is bad, none of the components will work.
INTEL i7 930
3x2gb Corsair Dominators
EVGA GTX 480