Uninstall Windows Messenger
Click Start > Run and in the Open: box type the following command (press OK when done):
RunDll32 advpack.dll,LaunchINFSection %windir%\INF\msmsgs.inf,BLC.Remove
You can just copy/paste the command above in the Open: box from the Run command.
Note: If you have Windows XP Service Pack 1 installed, you'll receive an error message. Just click OK, Windows Messenger will be removed anyway.