A mounted drive in a backup set is also backed up unless you tune your backups to prevent this occurrence. You can mount a volume to as many paths as you want, or you can mount a volume to a drive letter and a path. The only restrictions are that the folders you mount the volume to must be empty and not mapped to other volumes, and they must be on NTFS volumes on the local computer. You can't mount volumes to network-accessible drives. You can visually distinguish ordinary folders from mounted volumes by the icons that Windows Explorer uses for them.
Ordinary folders have the familiar manila folder icon, whereas mounted volumes have a drive icon.
Mounted drives are useful because they eliminate the 26-letter restriction on logical drive names. In addition, you can use mounted volumes to enlarge an NTFS volume on a basic disk, and you can use mounted drives to make part of an ordinary volume fault tolerant. If you mount the new volume, as Screen 2 shows, you can enter a drive path or click Browse to select a new volume from the available choices, as Screen 3 shows. If the drive you select doesn't have an empty folder you can mount to, you can click New Folder and enter a name to create a new folder. Finally, Disk Management offers you additional flexibility for naming drives and volumes.