hmmmmm, not sure if you can. Maybe, if you were willing to learn open firmware commands. If holding "C" doesn't work, I'd say pull the HDD, buy a laptop IDE to IDE adapter, drop an OS on it from another computer, and go to town. If you can't do that, you could try buying a messed up mactop off of eBay and doing a HDD (from similar model) and/or CD transplant (from very similar model).