Disable Windows Explorer's default context menu
User Configuration\Administrative Templates\Windows Components\Windows Explorer
Description
Removes shortcut menus from the desktop and Windows Explorer. Shortcut menus appear when you right-click an item.
If you enable this policy, menus do not appear when you right-click the desktop or when you right-click the items in Windows Explorer. This policy does not prevent users from using other methods to issue commands available on the shortcut menus.