I have found some problems cloning to USB that go away if the process is carried out inside of the PC that the drive is to eventually reside in. In other words, I wonder what would happen if you had put the 320 into the PC, cloned the 40 to it and then just removed the small drive. I'm willing to bet the 320 would have booted properly. I don't clone to USB drives but will create a compressed image on them that can later be restored to a disk that's in the PC. I've never had a problem with that method and have used two different cloning/imaging utilities over the years.