My iMac is Stuck in Sleep Mode!

Last night I came home and my computer was stuck in sleep mode, and the CD drive was clicking, like it was trying to load a disc. So, like an idiot, I put a disk in thinking that would solve all my problems. The clicking didn't stop and I couldn't get the disc out or wake my computer up. I held down the power button, unplugged it from the wall, all that good stuff... nothing. It's like it doesn't even know it's getting shut off. As soon as I turn it back on it goes right back into sleep mode. Since last night the clicking has stopped, but the computer will not come out of sleep mode.

Basically what I'm looking at is a black screen but the light is on.

I have a G4 Intel iMac.
160GB
1 GB of RAM
2 GHz (I think)

PLEASE HELP I need this computer to work!

Reset the power management. On that machine you have to remove the bottom cover, there is a small recessed button next to the wireless card slot. Push it for about a seccond.

My fault. It's a G5 with iSight, not a G4.
I followed the instructions for resetting the power management here:
http://docs.info.apple.com/article.html?artnum=301733

Now my computer isn't in sleep mode but after I pressed the power button the fans came on full blast and the computer is not starting up.