How to set disk D for auto-backup?


My PC has two disks, C and D. the software can backup the file on diskC expect ‘system’. When I select ‘D’, the software treat it as ‘system’. In fact there are all data on disk D. WHY? How to solve this problem. For me, it is more important to backup D than C.  


What is the backup software tha you are using, is it the WD Anywhere Backup or the WD Smartware?