Do you have the reinstallation disc for your 2008 iMac? If you do, you can still get Leopard onto that G4 iMac. Using Disk Utility on the 2008 iMac, make another partition on its hard drive. Install Leopard onto that partition using its reinstallation DVD. The retail Leopard DVD will not work as it is too old to support that iMac. Once the installation is complete, run Software Update and update everything. Trust me, update Leopard on the 2008 iMac instead of the G4. In Disk Utility on the 2008 iMac format the G4's hard drive with HFS+ and AMP with it in Target Disk Mode. When the formatting is complete, start CarbonCopyCloner and clone the new Leopard partition from the 2008 iMac onto the G4 iMac. Once that is done, you can startup the G4 into Leopard and remove the extra Leopard partition from the 2008 iMac.