You can create a System Image of multiple drives.
Control Panel > Backup and Restore > Create a system image.
On the next screen you select the target drive to receive this multiple-partiton system image. Select a target and click NEXT.
On this screen, the OS drives are greyed out as they are PREchecked for you (you must back them up). You can select additional drives. But, obviously, you can't select a drive that you're using FOR the backup (I assume if the prior screen had G selected for target, G won't be shown on THIS screen).
As an aside, I did a system image, by accident, that included my D data partition.