To remove windows messenger from your WinXP Machine you'll have to open the %systemroot%\inf\sysoc.inf file for a little editing. Each line in this file is a Windows component that´s installed on the machine. Find the line that reads:
msmsgs=msgrocm.dll,OcEntry,msmsgs.inf,HIDE,7
Remove the word HIDE and remove all spaces between the two commas. So it looks like this:
msmsgs=msgrocm.dll,OcEntry,msmsgs.inf,,7
After you restart your system, go back into the Add/Remove Programs Control Panel applet and you´ll see the MSN Messenger utility. You can now remove the program as you normally would any other.
Or you can try what Microsoft Suggests
http://support.microsoft.com/?kbid=302089
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Another way
1. First, right click the Messenger icon in the system tray and click Exit.
2. Right click the Start button and click the Explore command to open the Windows Explorer.
3. In the Windows Explorer, expand the Program Files folder on the partition where your operating system is installed (the partition that holds the WINDOWS directory) and right click the Messenger folder and select Rename.
4. Rename the folder to MessengerDISABLED and press ENTER to commit the name change.
5. Restart the Computer. No more Windows Messenger