Any computer dudes out there?!?! Help!

O.k... Now I have a car that don't run, and a computer that don't run! This sucks!!

First of all... I turn on the computer and NOTHING happens! No fans, nothing! So I replaced the Power supply... Still nothing! I replaced the motherboard... Still nothing!! WTF?? Am I forgetting something stupid? Can someone help me out here? I feel like I am just throwing money away.

The green light is on the motherboard... but that is it! I even tried a different switch from a different computer, still nothing (Unless that switch is bad too??)

A bad CPU wouldn't do this, would it? I should still get fans to work, a beep or something??

Thanks much!!