I disconnected the optical drive cable and tried booting up. The HD spins, the screen lights up, and it sits with small flashing folder in the middle of the screen, which alternates between a ? and a happy face icon. I tried this with no keys pressed and with the C key pressed, same result.
If I leave the optical drive disconnected, and connect a USB optical drive, do you think it would try to boot from that? I've already tried booting from a USB HD, that has OSX 10.4 on it, and it does not recognize it.