My brother (computer technician) said that more than likely you fried your motherboard. Which means, you need to buy a new one and a new power supply. "But why a power supply?" Because it's a short in the power supply that causes the motherboard to fry. If you keep it, then put a new motherboard in, it will fry too.
However, this is based on very little since you haven't really told us anything other than a black screen.
Do lights on your keyboard work? (Caps lock lights, scroll lock lights, etc.)
Is everything plugged in?
Do you see anything flash at all on the monitor when turning it on?