How to Restore backup from external drive to itunes or iphone in Windows 8?
iTunes doesn't work with symlinks very well. Try to copy the backup of your device back to "~\MobileSync\Backup" folder. Your backup is a folder in "Backup" folder with 40 random chars in name (device UDID).

After copying the backup, restart iTunes. It should now see the backup and allow you to restore it.