I have a Mac Mini G4 that I am working on, but I have not run into this issue before. The Mac Mini boots either to a screen that says to reboot or to a grey apple screen and a spinning circle. So I am trying to attach it to a Power Mac G4 (10.4.11) in target disk mode. I can start the Mac Mini in target disk mode and it seems to be stable, however, when I attach it to the Power Mac the Target Disk logo stops moving on the screen and then the Power Mac can see the drive, but it will not let me do anything and eventually it unmounts the drive. I am attaching them together over firewire. The ultimate goal at this point is to run disk repair on the Mac Mini, unless anyone thinks the HDD is dead and I should just replace it. Right now I am leaning towards dead HDD.