Apologies for the brevity of this post, but I have to dash.
However I hope the links given below will clear up the situation.
How to Disable Windows Messenger (Instant Messaging Chat)
Including how to stop OutlookExpress from calling it
http://www.pchell.com/support/removemessenger.shtml
How to Disable Windows Messenger Service (IP Based messaging)
http://www.pchell.com/support/ipmessaging.shtml
To paraphrase a white rabbit
I'm Late, I'm late, for a very important date.