changing sign in

Somehow Windows Messenger (running XP) is signing in with
my attbi email. That will soon change to comcast. I
want to use a different email from a different server.
Nothing I have done so far will change or give me a
choice. It says I have a passport for a different email,
but it is not in the sign in with another whatever.
Also, I can not get the website for help to stay unless I
hold the control key and even then it pops out. Any help
on these issues would be appreciated. Thanks