I just got a iMac G5 (pre iSight) and I'm trying to start it up holding down option while it's connected to a duplicate version of my MacBook's HD on an external firewire HD and it's not being able to boot from it . My Macbook works fine when I do this if I feel like trying something out on the external drive 1st . The only thing I can think that's wrong is that the G5 & Intel HD's are not swappable . This could ruin my plans of putting a drive in the iMac the same size as my Macbook and simply copying over all the contents through restore w/ target disk mode . Is that what I'm dealing w/ ? And if so does anyone know a way around it besides having to reinstall all my old programs and files into the G5 piece by piece ? FYI : My intel MacBook is still running Tiger and that's what's on the iMac as well . Sorry for the newbie post and I did try a search . Thanks .