windows live messanger?

Hi,I have recently got a new computer with WINDOWS7 and after log in I get the Windows live messenger sign in box popping up,I don't want it or use it(my e-mail is with tiscali)how do I remove it and the shortcut at the bottom of the screen as it is annoying having to "x" it all the time.My wifes e-mail is " at live", will it affect her normal e-mails.Any help please.