http://en.wikipedia.org/wiki/Power_s...unit_(computer)

Does the power supply fan come on?
You can test the power supply with a volt meter if you have one, see the wiki.
Be careful.

If you touch anything inside the computer, take the following precautions:
Don't do it on carpet, STATIC KILLS
Since the power supply is in question, do not leave it plugged in.
Sometimes I leave it plugged in and hold on to the case to ground it.
Touch the case before working on any components.

30v will kill your motherboard. Now how many volts it takes before you can feel it depends on other factors like Amps. However, you could kill the motherboard, not feel it, and thus likely not even know.