help! mac freezes at startup!


When i start my g5 the mac logo screen comes up and the status bar freezes just shortly after it starts. Underneath it says, "Starting mac os x."

i tried to boot from the originial apple hardware test cd, original install cds, and held the C button, but it goes back to the problem screen i jus mentioned. same thing happens when i try to boot in safe mode.

i tried to reset nvram but OF asks for a password when i type reset-nvram and i don't know it.

what can i do to fix this?