When you try to mount a backup of a volume that contains files that use deduplication you may receive an error like the following:
Error 0x80070780: The file cannot be access by the system
This is due to folders on that volume containing files that have NTFS file attributes that are junction points to any deduplicated files.
Unfortunately if Windows does not have the deduplication role enabled these NTFS file attributes do not function correctly on a mounted volume.
The fix is to ensure the Windows deduplication feature role is installed as this article describes.