OS X (Apple)

I made a tragic error and erased the extensions manager from my IMac. Now, I can't get the computer to boot up. It just stays on the gray screen. I've tried using the open apple+s method, which brings up the command console (not sure if I've got the lingo down right), and I've tried everything, but nothing works. I need to be able to reset the system so I can go in and reinstall the os (os X Leopard). Any advice here? I'm like a blind person wandering the streets of NY in search of a needle here.

Thanks in advance

c, or perhaps apple-key-c, will cause your mac to try and boot from cd/dvd instead of hard drive.

I actually tried that many times, but each time, the computer just spits the disc out. I've also tried booting in safe mode+v, but once the screen is full, it just stops and does nothing else. I've been looking for some sort of method, using unix command prompts, to try and erase the computer, or reset everything, or at least be able to get into the computer. I know all the hardware was working before I erased the ext mgr, which I did to try and get rid of what I thought was a virus. Turns out, it wasn't.

That doesn't sound right. Which disc?

It's the disc that came with the computer.

Asked my mac-user friend, and he says it means that model doesn't understand c or apple-c, and you should be holding down 'option' on boot instead.

I held down the option key, and all it shows is an icon for the hardrive, but not the cd.