When Windows SteadyState is first installed, Windows Disk Protection is turned off by default and does not use any hard disk space on the system drive. When turned on, Windows Disk Protection creates a cache file to save all changes to the operating system and program files. The cache file that is created will reserve a significant amount of space on the system drive.
Windows Disk Protection should remain turned off until you are ready to use it. After you install and turn on Windows Disk Protection, turning off Windows Disk Protection will remove the cache file created upon its installation. Turning off Windows Disk Protection effectively uninstalls this protection feature.