sorry.. I don't quite follow you.Take it out of the case and put it on a non-conductive surface, wood, cardboard. And see if it starts at all, using your PSU, of course. You can use a flathead screwdriver to short the two pins that turn on the computer.
"short the two pins that turn on the computer"
there's a 2 pin wire labeled Power SW. I assume that means Power Switch and one is labeled with a "G" (ground ? ) and the other with a triangle.
edit: or do you mean something like this?
Overclockers Hardware - Overclockers Hardware - How To: Test PSU Voltages