iMac G4 keeps shutting off.

[devilsfan1986]

i was just given an iMac G4, and it's having a problem. When i first received it, the computer would flash an icon of the Earth. Then it would flash a pic of a folder with a question mark. And finally, it would go to the gray Apple screen, attemp to load the OS, then just shut down. I tried a few tricks like refreshing the ram or memory. That at least took the flashing pic of the earth and folder away and goes right into the gray Apple screen. But alas, it keeps shutting down. I also tried the whole "command c" trick. I can get into the firmware, eject the cd door and put a restore cd in, but once i go to "mac-boot" it goes back into the gray Apple screen and shuts off. The cd is working because I can hear it loading once it goes to boot. I did read here that someone replaced a hard drive and it solved there same problem. Any ideas? Is there anything elsi I can try?