Disable Windows Messenger(MSN)

Warning If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

Windows Messenger 4.0 or later versions on a Windows XP Professional-based computer

To turn on the Do not allow Windows Messenger to be run option, follow these steps: 1. Click Start, click Run, type gpedit.msc, and then click OK.
2. In Group Policy, expand Local Computer Policy, expand Computer Configuration, expand Administrative Templates, expand Windows Components, and then expand Windows Messenger.
3. Double-click Do not allow Windows Messenger to be run, and then click Enabled.
4. Click OK.
5. On the File menu, click Exit to quit the Group Policy snap-in.

Windows Messenger 4.0 on a Windows XP Home Edition-based computer

Change the preferences in Windows Messenger. To do this, follow these steps.

1. Start Windows Messenger.
2. On the Tools menu, click Options, and then click the Preferences tab.
3. Click to clear the Run this program when Windows starts check box, and then click OK.

Outlook Express

1. On the Tools menu, click Options, and then click the General tab.
2. Click to clear the Automatically log on to Windows Messenger check box, and then click OK.

Outlook 2002

1. On the Tools menu, click Options, and then click the Other tab.
2. Click to clear the Enable Instant Messaging in Microsoft Outlook check box, and then click OK.

Windows Messenger 4.5 or later versions on a Windows XP Home Edition-based computer or on a Windows XP Professional-based computer

1. Start Registry Editor. To do this, click Start, click Run, type regedit.exe, and then click OK.

If the following registry subkey already exists, go to step 6:
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Messenger\Client

2. Click the following registry subkey:
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft

3. On the Edit menu, point to New, and then click Key. Type Messenger for the name of the new registry key, and then press ENTER.

4. Click the following registry subkey: key:
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Messenger

5. On the Edit menu, point to New, and then click Key. Type Client for the name of the new registry key, and then press ENTER.

6. Click the following registry subkey: key:
HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Messenger\Client

7. On the Edit menu, point to New, and then click DWORD Value. Type PreventRun for the name of the new DWORD value and then press ENTER.

8. Right-click the PreventRun value that you created in step 7, and then click Modify. In theValue data box, type 1, and then click OK.

9. Quit Registry Editor.

More info on Microsoft Support