You might have to "breadboard" your computer, aka take it out of the case, put it on some non conductive surface, and build it on that so you can do some testing. You should google the make of your motherboard and find out where your power pin connectors are, take something metal like a screw driver, and lightly tap them. That will give them enough voltage to start up. If that doesn't make it start, your motherboard might be dead.