I sold my MBP in Nov. I had used about 120GB of a 320GB external backing it up with Time Machine. The last backup was Nov. 3, 2010. I purchased an iMac on Dec. 2, and restored it from the latest Time Machine backup which was, again, Nov. 3. There were many other backups before the Nov. 3, dating back to at least May 2010, and a few new backups up to Dec. 7. I had some issues with my iTunes library and got several folders moved around. So last night I decided to restore the iMac back to the Nov. 3 backup. Once the iMac was restored, I chose the same external to back up with. Time Machine did it's thing, and then told me that the backup disk was full, and that it deleted old backups; and the oldest backup available is Dec. 4!! Why did it have to go back that far and delete so many backups, including the Nov. 3 backup? I know for a fact that the Nov. 3 backup was exactly the way I needed my files and documents set up. I didn't lose anything, but I'm just curious as to why it deleted so many when the 320GB wasn't used up anyway.