Show Hidden Files and Folders - Folder View Option
Registry Key Located At:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced\Folder\Hidden\SHOWALL
CheckedValue  should be REG_DWORD. Value should be 1. If 0 whatever user tries to enable will not save or apply. If 2 both options will be selected, you can select one by pressing but it will not save once you press apply.