I think for whatever reason you're getting this error, maybe corrupted file, maybe a result of improperly deleting a system image, maybe a result of trying to manually delete the
MediaID.bin file, whatever.
I suspect that users not knowing about (and using) the backup utility's "manage space" feature (seen in the utility's main window, once any backups are created) probably is causing issues with backup and restore, especially since users report difficulty in trying to use explorer to manually delete Windows 7 backup files.
I suggest that at this point, it's pretty likely that opening manage space and deleting the system image, might clear the backup-restore utility's issue with the MediID.bin file.
I wish MS afforded reasonably readable and useful instruction for this utility (as well as most other's as well), but I suspect if the MediaID.bin needs or should ever be explorer (manually) deleted, I suspect it shouldn't and likely Windows will make every effort to prevent it (so long as it's a valid file).
So as the MediaID.bin file is miniscule, I'd say leave it alone because it probably has an integral relationship with the backup-restore utility's proper functioning.
The most I'd do (after say, properly deleting a system image file) is to maybe delete the explorer listed WindowsImageBackup file (which I think at that point is merely a 'remnant of the "system image" file).
I see some users reasonably question explorer's indications that their backup files are zero bytes. In that it's otherwise obviously that Windows 7 backup files aren't fully explorer supported, so towards properly managing backup files (even just to set your mind to rest that the backup files are NOT zero bytes), simply use the manage space feature to check on their sizes.