Thanks, dialabrain. I tried that link but it hasn't helped much. I understand that the OS isn't usable, but it should be! It came from the universal Panther install CDs, on to a healthy HD just reformatted. The G4 (that I did the installation on) would have thought I wanted to use it IN the G4, not in a G3, but could that be the problem? If not, what could possibly be wrong? The G3 is capable of running all OSs in X series up to Tiger. I don't have a replacement CD drive in the G3, but I wonder if I should move the G4's CD drive over to the G3 and try to re-install Panther - what do you think?