OK I have done my homework and located an appropriate firewire cable and my iMac can now see the Powerbook which is happily displaying the firewire connection icon.

However, it looks like I will have to reinstall the system software and I can't work out how to boot the G4 from the iMac using the install disc inserted in the iMac. I don't want to kill my iMac doing this job so could someone kindly talk the idiot (me) through the process please?