Downloaded SuperDuper and backed my primary hard drive up to an external Seagate HD connected with USB-2. Everything seemed to work fine as the entire contents of my primary HD in the iMac were transferred and the external HD was set up as a bootable drive by SuperDuper. Everything looked good until I tried to boot from the Seagate external HD. I held down "OPTION" and pressed the power button on the iMac. A small window came up and asked which drive I wanted to boot from. I selected the Seagate and the system started. It got as far as the gray apple in the center of the screen and the little rotating-spoke wheel underneath and continued in that mode for 30 minutes. Finally I shot the iMac down and rebooted from the primary HD. That all worked as expected. I am guessing that USB-2 just has a problem as an interface for bootable drives ? ? ? ? Any suggestions would be appreciated.