I'm upgrading my iMac (running 10.3) to sell to a friend, and after replacing the original 4 GB harddrive with a 13 GB IBM I had sitting around the machine refuses to boot from the hard-drive. So, I tried another drive, and alas got the same result. So, I dropped the original HD and the iMac boots fine. What can I do to get a newer, larger capacity drive to work with this iMac? Any ideas would be appreciated.