Good news and bad news. Both hard drives in the G4 Tower have gone bad - at once. I had not used the G4 Tower for a couple of weeks as the mouse's cord was fraying. So, when I went to boot up, I got the folder with a question mark on it. I guessed that the boot drive might have go corrupted so I went out and bought a new mouse and OS X 1.4 Tiger.
Tiger is loaded on my PowerBook and it seems to be a good upgrade (I am even now upgrading to 10.4.1). The widgets will take some getting used to (many seem to be rather gimmicky) while Spotlight is incredibly fast.
My work around for the G4 was to load OS X Tiger on a firewire hard drive coupled to the PowerBook. This then allowed me to boot up the G4. A quick look at disk utility confiormed that one drive was failing the other has failed. Luckily no data is lost as the G4 is basically our backup computer.
So I guess I need to buy another hard drive. . . .