I have an old G5 that I am rebuilding. I am using the Mac OS x v10.2. I bought a brand new apple keyboard but unfortunately the keyboard is not working when I plug it in so I can press and hold "c". I am guessing it isn't working because the keyboard is not loaded onto the computer. The computer comes on to the grey screen with the folder icon with a smiley face and flashes to a "?". Is there ANY WAY I can load the OS to the computer without the keyboard working?
Remove the power connector from the hard drive. The computer will boot from the CD (eventually - it may take a minute or two). Then, if you feel brave, you can hotplug the hard drive and continue.
But I agree that you have other problems. The keyboard should work at boot (else there would be no point in the "hold down C bit"). Have you tried it in more than one USB port? Have you tried a PC keyboard?
If you want to check the keyboard, just hold T during powerup/startup and it should go into firewire target mode, I have found that sometimes the optical drive fail but you maybe able to use a standard pc optical drive to install your os.