IMac :: Won't Boot Up - Unreadable Cd Stuck In Drive And Eject

My Intel based imac (purchased in Sept 07) won't boot up because there's an unreadable movie dvd in the disc drive that won't eject... when I turn on the computer, all that happens is it plays the opening chime and displays a white screen... I'm wondering if someone can help or suggest what's going on: Basically I put a movie dvd in my imac that my regualar dvd player wouldn't play so I thought I'd try it in my imac. Once inserted, the disc drive tried to read it but it wouldn't mount, it just made an odd spinning/grinding sound. It wouldn't eject using the keyboard eject button so I shut down my computer so that I could call a friend to ask for advice.

My friend gave me several options to try - holding the left mouse button at start up, hold C down on keyboard, command option O F to open firmware, reboot pram but non of them work. Basically when I start my imac it immediately tries to read the unreadable dvd and doesn't get to the normal start up procedure, it just shows a white screen and chokes on the dvd. Is there a way to manually eject the cd or does the machine have to be opened up and the cd physically removed? Is it likely that my imac will start up normally once the unreadable dvd is removed? I hope my hard drive hasn't gone bad because I haven't backed it up in a long time... Is there a strong possibility that my hard drive is toast?