How can I block users from accessing the Microsoft Web application service that determines unknown file extensions?

A. By default, if you try to open a file that has an unknown file extension, you'll be given the option of selecting a program with which to open the file or using the Microsoft Web service to help ascertain the required application to open the file type, as the figure shows. To block the Web lookup of extensions, perform these steps:

1. Start the registry editor (regedit.exe).
2. Go to the HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\policies\system registry subkey.
3. From the Edit menu, select New, DWORD Value.
4. Enter a value name of NoInternetOpenWith and press Enter.
5. Double-click the new value and set it to 1. Click OK.
6. Close the registry editor.

The change takes effect immediately, and the user now sees only the dialog box for choosing the application to use; the option to connect to the Web service is gone.