Registry settings for certain protocols are overwritten, and Communicator 2007 becomes the default application for these protocols when you log on to Communicator 2007

When you log on to Microsoft Office Communicator 2007, registry settings for certain protocols are overwritten. These protocols include the following protocols:

• TEL
• CALLTO
• SIP
• SIPS
• IM
• CONF

Additionally, Communicator 2007 becomes the default application for these protocols.

This issue occurs because, when you log on to Communicator 2007, the registry entries for these protocols point to the location where Communicator 2007 is installed. Therefore, Communicator 2007 becomes the default application for these protocols.

To resolve this issue, follow these steps.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:

1. Exit Communicator 2007.
2. Install update 951662.
   
   For more information, click the following article number to view the article in the Microsoft Knowledge Base:
   951662  (http://support.microsoft.com/kb/951662/ ) Description of the update for Communicator 2007: April 30, 2008
3. Click Start, and then click Run.
4. Type regedit in the Open box, and then click OK.
5. Locate and then right-click the following registry subkey:
   HKEY_CURRENT_USER\Software\Microsoft\Communicator
6. Point to New, and then click DWORD Value.
7. Type DisabledProtocolHandlerRegistrations as the name of the new registry entry, and then press ENTER.
8. In the registry, enter the correct information for the application that you want. For example, to change the application for SIP from Communicator 2007 to the application that you want, follow these steps:
   1. Locate and then click the following registry subkey:
      HKEY_CURRENT_USER\Software\Classes\sip\shell\open\command
      Notice that the default value points to Communicator 2007.
   2. Double-click the Default registry entry. Then, modify the value to reflect the application that you want to use instead of Communicator 2007.
9. Prevent Communicator 2007 from being rewritten to the registry setting that you modified in step 8b. To do this, use the values in the following list for the DisabledProtocolHandlerRegistrations registry entry that you created:
   • TEL: 0x0001
   • CALLTO: 0x0002
   • SIP: 0x0004
   • SIPS: 0x0008
   • IM: 0x0010
   • CONF: 0x0020
   When you enter the appropriate value for the protocol for which you want to use another application, Communicator 2007 will not be written to the registry when you log on.
   
   This registry entry is a bitmask. Therefore, you can sum the values in the list if you want to prevent Communicator 2007 from being the default application for multiple protocols.
   
   For example, to prevent Communicator 2007 from being the default application for SIP, enter 0x0004. To prevent Communicator 2007 from being the default application for CALLTO, enter 0x0002. To prevent Communicator 2007 from being the default application for both SIP and CALLTO, enter 0x0006.
   
   To prevent Communicator 2007 from being the default application for all the protocols, enter 3f.
   
   Note These values can be changed only after you log off from Communicator 2007. If you change the value in the DisabledProtocolHandlerRegistrations registry entry while you are logged on to Communicator 2007, there is no effect.
10. Log on to Communicator 2007. Verify that Communicator 2007 has not overwritten the registry data for the protocols that you modified in the previous steps.
    
    For example, if you are using a different application for SIP, verify that that application remains in the registry under the following registry subkey:
    HKEY_CURRENT_USER\Software\Classes\sip\shell\open\command
    Also, verify that the value in the DisabledProtocolHandlerRegistrations registry entry is correct. For example, the value for SIP should be 0x0004.