My G4 starts up fine from the hard drive. It just doesn't see the CD drive. Never shows up on desktop. I restarted with option key down, but it never shows up. I checked seatings of cords -- seem to be in there okay. Neither System disk, or data disk, or audio disks show up. Power supply appears to be working, as it winks in a pulse-like fashion during start-up, then just stops. Could this be a software problem? Is there something in System Profile I should look at, i.e. extensions? Advice?