When you say you get nothing, does that mean that no sounds, no lights, no hard drive spinning up. Or does that mean that everything comes on and the monitor doesn't turn on. Usually, if the cpu fan is faulty or misconnected, your computer will still fire up, but you will get some beeps from the POST. That is not always the case though so it might be the fan. But for sure tell us what is actually happening when you press the power button.
As the sun sets, the earth shall prepare