Administrators Can't Remove All Users from Built-in Groups

SYMPTOMS

If you are an administrator for Windows NT 3.50 or a 3.51 Workstation or standalone Server, and you try to delete all the users from built-in groups such as Administrators, you will get an error message that says the action can't be performed on built-in groups.

On domain controllers, however, the administrator can delete everybody from every group. The built-in groups and accounts can't be deleted, but all the users can be removed from the group.