Windows Messenger is an instant messenger that is built into Windows, completely separate from MSN Messenger, and more of an annoyance than anything else. If you click here you'll find instructions for disabling and removing Windows Messenger, which should do the trick.
Hope this helps,
John
I just restored my Windows XP Pro and I now have 2 messengers? One is MSN Messenger which I use alot but as of today a messenger called "Windows Messenger 4.7" is now on my task bar next to my MSN Messenger 7.5? How do I get rid of the "Windows Messenger 4.7"? Please help and all help is deeply appreciated. God Bless.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic