I am running a differential backup at 3pm every day ad the archive folder is getting full. Today I ran a full backup with the intention of deleting the "old" full, and "old" differential backups. Is this acceptable, and can I just delete those files leaving the "new" full and any "new" differentials? Ie., does the program know that it's doing a differential on the last full backup? ATI 11 backing up on a USB external HD.