I have three computers networked.  Two systems have Windows XP and one
Windows Vista.  Windows Instant messenger is installed on all three
systems. The computers are setup with a user account for user "A" on
all three systems.  Until recently there was only a single hotmail
account on these system for user "A".  Last week I created an email
account for my wife, lets call her user "B".

Windows Live Mail is also the mail program on all three computers.  We
each have an email address with our ISP.  As mentioned above we each
now have a Hotmail account.

Now for our problem and hopefully someone can give us a solution:

Since I created a hotmail account for my wife whenever any of the
three computers boots up Windows Live Messenger opens with my wife's
Hotmail accounts.  If I try to sign her out and sign myself in her
sign out is executed but Live Messenger immediately  sign her back in.
I can now never be signed in as a Live Messenger user even though we
each have an account.

Can someone please tell me how to fix this situation in step by step
detail?

Thanks