[FrankEEE]

did you try 'zapping' the PRAM on startup (COMMAND+OPTION+P+R)? Another thing you could try (if nothing works) is attempting to reset OPEN FIRMAWARE - procedure:
Startup holding COMMAND+OPTION+O (oh not zero)+F
At the prompt type
reset-nvram
set-defaults
reset-all
(remember that this mode will use the US keyboard layout)
the machine will boot and you will see!

Hope this helps.
Frank.