Saw this question on the G4 Digest so I'm late in responding. If you have another Mac and a Firewire cable you can try rebooting your G4 in Target Disk Mode. If it actually connected at all to the system the odds are fair that it will show up as a hard drive on the master computer and you can try ejecting it from there. On the other hand it's been a while since I used Target Disk Mode and there is a nagging feeling in me that says it only allows access the main drive....