The Windows Backup wizard wants all targets present at the time of configuration. Since we only have one dock (and a minimum of two drives), if we try to add additional hard drives to the job, the wizard fails with the error: “The filename, directory name, or volume label syntax is incorrect” and the backup job is not modified.
This can be achieved in simple steps.
Find “Command Prompt” in the start menu and “Run as Administrator” from the right-click menu.
Get the drive ID of the disk we want to add to the job as we’ll need it for the next step:
At the command prompt, type wbadmin get disks
Each drive attached to the system will be listed; so, find the removable disk and copy the long string of numbers (and the brackets) that make up the “Disk Identifier” Copy this to the clipboard
At the command prompt, now type WBADMIN ENABLE BACKUP -addtarget:{PASTE-YOUR-DISK-ID-HERE}
You’ll get a one or a bunch of prompts (depending on if the drive is formatted for backups or not, if existing backups are present on the disk, etc.)
Finally, make sure you answer Y to the question “Do you want to enable scheduled backups with the above settings?”
Now, when you look at the Backup screen, you’ll see multiple targets in the DESTINATION settings, and the Destination Usage drop down will show the drive that’s connected PLUS the disconnected drive.