12-01-2007, 10:13 PM
The drive needs to be reformatted using disk utility prior to cloning to it. IIRC, the drive format for Leopard should be GUID for it to be bootable. Boot from your Leopard DVD as if to install, switch to Disk Utility and pick the external drive to format it. Once the formatting is complete, quit the installer and reboot to the internal drive. Then clone your boot disk. Should work.