This setting can be used to disable the integration of Windows (MSN) Messenger so that is does not start when using Microsoft Outlook.

To disable the Windows Messenger in Outlook, follow the next steps:

1. Open the Registry Editor click on the Start button on your taskbar, then click on Run and type "regedit" and click on OK to start the regedit utility.
    
2. Expand HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\10.0\Outlook\InstantMessaging (see picture 1).
   
   

   Picture 1

3. Create a new DWORD value, or modify the existing value, called "ForceDisableIM" and set it according to the value data above.
    
4. The modifications you made will be in effect after you logout or reboot your PC.