will ghost 15 only backup to one external hard drive, everytime we try to switch backup destination hard drives it fails on the other hard drive. We have 2 so one is always stored off site. These external hard drives are both brand new, and I even reformatted the one that keeps failing in hopes that that was an issue. We are doing a complete backup of the computer each and everytime, and the external hard drives are twice as large as the computers hard drive, HELP PLEASE