I just pulled a 2 TB HDD that was connected via USB to my imac out of the WD external HDD inclosure. I poped it into my new mac pro and when I booted it said the drive was unreadable. any recommendations? also I transferred everything from the iMac via time machine. I have alot of home pictures/movies on this drive; formatting is not an option. BTW disc utility shows no options for first aid.