If several people use a machine to sign into MSN or Windows Live Messenger then their email addresses may be added to the MSN login dropdown list presented when you come back and login later. How to delete email addresses, MSN user names and passwords from that list for privacy reasons?
In "Windows Live Messenger" is an option "Remember me" and below is "forget me" in blue color you can click on that. Then that name or id in the box will go off ( it will ask for confirmation ), also uncheck "sign me automatically" tick box. After you can sign with your new MSN user name and password.