HOW TO: Remove/Uninstall windows Messenger
On a Windows XP system
Click Start > Run
Type the following text (Or copy and paste it into the command text box)
RunDll32 advpack.dll,LaunchINFSection %windir%\INF\msmsgs.inf,BLC.Remove
Click OK
Windows Messenger should be successfully removed
source : http://www.dougknox.com/xp/tips/xp_messenger_remove.htm
with your OpenID.
If you do not know what OpenID is,