Only 1 thought comes to mind.
Unplug everything from the back of the computer
Press and hold in the start button for 45 seconds (minimum)
Plug everything back in EXCEPT the phoneline and restart the computer.
Once restarted plug in phoneline & do a reboot.
This will help IF the computer and the keyboard are not internally damaged in some way.
Since I installed Windows XP, my computer occasionally makes an odd noise and freezes. When I restart, the keyboard doesn't work. The problem fixes itself in about a day, but it's still pretty annoying. Any thoughts? Thanks.