Disable File Association Change

Admin Tip #200: Disable File Association Change

Hits: Failed to execute CGI : Win32 Error Code = 3

If you want to lock down an association so it can not be changed:

Find the association to lock under HKEY_CLASSES_ROOT
In the right panel, create a new binary value assigning it value=01000000

The application associated to the extension is now locked and can not be changed except by removing this value. When you go to the Folder Options / File Types screen, you won't see that file type listed.