iTunes & Drive Space
iTunes requires a great deal of free space when restoring an iOS device. Encrypted backups build an unencrypted copy of the data, as it loads it back to the device. You will need at least enough free space to match 200% of the backup you plan to restore. Backups are located here: C:\Users\%username%\AppData\Roaming\Apple Computer\MobileSync\Backup or C:\Users\%username%\Apple\MobileSync\Backup