C only beeps & no longer work

I'm running Windows Me and whenever I do CTRL C, the computer only
beeps. Nothing is copied. This is the case regardless of which
application I try this in.
Also, CTRLALTDEL no longer displays the Task Manager.
ALTPRTSCN doesn't work either.
They were all working this morning, and then all of a sudden, they
stopped working. I have rebooted my computer and done a virus scan.
Same problem.
The keyboard is working fine as I've hooked it up to another PC and
tested it.
If anyone can help I'd appreciate it.
Thanks.