304 Keyboard or system Unit Error

Bonjour,
problem and attempted remedy:
recently i tried installing a new mouse after I noticed that my cursor failed to move as directed and also failed to print the typed letters on the screen.

after remedy taken:
after I shut down the computer and replaced the old mouse with an IBM compatible one for my Compaq, I got the following mssg when I turned the computer on:

"304 Keyboard or system Unit Error"
"F1 Boot and F10 Computer Set Up"

I tried hitting F1 and the computer did not respond.
I then tried hitting F10 and again no response.
I even tried control + alt + delete and again no response.
I tried shutting it off by hitting power and restarted it, but again the same error message appeared.

Please HelP!:
I'm at wit's end. Would greatly appreciate any helpful hints.

Thank You