Only a white screen when powerbook g4 is turned on

[optionel]

I really hope someone can help me....

Basically, my powerbook froze when i tried to go back to watching a dvd i had in after i used safari to check something. Force quitting did not work and after it was pretty much frozen for awhile, i just turned off the powerbook with the power button. when i turned the power back on, i managed to get the dvd out but the screen just remained white and it did not go on to the usual screens. and it stayed like that for a really long time until i had to just turn it off again with the power button. a few hours later, i tried to turn it on again and its still the same white screen. i found my software installation cd and followed the instructions but that didn't do anything. my powerbook is just stuck on the white screen. Does anyone know what's going on and how i can fix it????

 

[CharlieJ]

Hold apple or alt (i dont remember) +Shift ^+p+r during boot up and then let the chime sound 3 times and hit enter

or:


apple +shift +o+f

 

[optionel]

the command option p and r worked but then my computer (powerbook g4) froze again and this time there is a constant buzzing. i try to boot it up again with the command option p and r and now that's not even working either. the buzzing won't stop. please tell me there is something else i can do, i have a feeling there's something more serious happening.....