|Wow, face it, you screwed things up royally.|
Depending on where on the motherboard you touched and the voltage in the wire, you either fried the power supply, the motherboard, or both and if you were anywhere near the CPU, possibly that as well. There are three voltages going into the motherboard, 12V, 5V, & 3.3V plus circuits within the motherboard carry signals that may be as low as a few millivolts (mV), so when a higher voltage enters a circuit that is intended to carry a small voltage, something burns out. If the the short happens along a main power supply line, the feed back will damage the power supply's voltage regulating circuits.
The way to test this would be to begin by pulling most components out of the system and bench testing the system using a new or known working power supply and just the basics. Here is a link to bench testing:
Sorry, but understand that this might be an expensive mistake.
You have to be a little bit crazy to keep you from going insane.