Your hard drive might be perfrectly ok. I had something similar happen to me just a couple days ago after an storm flickered the electricity off and on. I have my computer plugged into a power strip -- all I had to do was plug the computer into a different outlet.

The problem could be any one of serveral things -- most likely the computer is not getting any power. First, make sure it is plugged into an outlet that works! plug a lamp into the outlett just to test it.

If that is ok then the problem might be the power supply. But unfortunately most people don't have anything to test that.

If I were you I'd take the computer to a reputable computer shop, or to a friend that knows what he's doing and has the test equipment to work on it.