Well. ~Coxy, you were correct. I tried a USB hard drive, zip drive, and CD drive. No Luck. The Mac would see only the USB CD drive, but would not start the disk. I tried OS 8.1, 9.2 and 10.4.11 install disks, but none would boot. As the internal DVD combo won't even open using Command-E or via the keyboard, I'm afraid the problem is with the logic board.

You mentioned forcing the Mac to read the USB through Open Firmware. What would the command be for that?