Windows Messenger also checks for updates automatically, but Microsoft was at least kind enough to give the users the option to install the new version rather than performing a forced installation. You must have administrative privileges to install the updates on your computer.
There's no Group Policy setting to disable the automatic version-checking feature, but there's a way to prevent Windows Messenger from running on a computer. To disable the automatic updates, you need to hack the registry. Depending on your version of Windows Messenger, the location to add the key might be different.
Start the registry editor (regedit.exe).
Go to HKLM\Software\Policies\Microsoft\Messenger\Client.
Add the key PreventAutoUpdate and set the value to 1.
For Windows Messenger 4.x, you may have to go to HKLM\Software\Microsoft\MessengerService\Policies, add the key DisableUpdates, and set the value to 1.
Keep in mind that the above modification prevents only the automatic version-checking feature; it doesn't prevent Windows Messenger from running on your computer. To prevent Windows Messenger from running on your computer altogether, use the Group Policy. On a domain, you may want to use a domain policy. On a standalone computer, use the local group policy. Here's the procedure for a standalone computer:
On a standalone Windows XP computer, go to Start, Run, and type MMC.
In the console window, click on File and then select Add/Remove Snap-in.
Click on Add and select Group Policy in the Add Standalone Snap-in box.
Click Add, Finish, Close. Then click OK.
Go to the User Configuration section of Group Policy.
Locate Administrative Templates, Windows Components, Windows Messenger.
In the right pane, double-click Do Not Allow Windows Messenger to Be Run.
Click Enabled and then click OK.