As described in thread http://www.wilderssecurity.com/showthread.php?t=160487, I decided to use TI 10 Home, due to the implementation in this version of backup locations. On January the 6 I have built my backup location on my removable HD. The number of backups is limited to 12. I have defined my backup task too. The task makes an image of disk C: (System) It makes an image of partition D: (Users) on my RAID1 array The remaining partition of the array, F: (Data), has no backup The task save backups in the backup location and performs a validation after backups. The backup is Differential and a full backup is required after 3 differential backups. The task is not scheduled, because the disk disk is usaully off line. I usually schedule the task on saturday evening, I log out my user and hot plug the disk. Later I come back and use the PC while backup validation is in progress. I had a full backup on 2007-01-06, and 3 differential backups on 2007-01-13, 2007-01-20, 2007-01-27. On saturday 2007-02-03, I have made my backup as usual and I assumed to obtain a full backup. No: I have 4 Differential bacukps! I would like to have a full backup every 4 weeks and a weekly differential. What must I do to obtain the result I want?