If its a desktop or tower, try reseating the keyboard cable (and check that its not in te mouse socket.) If that fails to fix it, swapping the keyboard for a known good one.
If its a laptop try an external keyboard. If that fixes it you need to get inside the laptopn and check connections.
BTW. No one reading this knows what you know so it helps if you put a little more detail - like what kind of PC is it. In fact I have assumed that it is a PC.
T, November 2006
