...MSN messenger for your PC, exactly the same thing also by mircosoft, allowing the same functions, (i believe that windows messanger only has the added bonus on corporate messenging which your not using in a home system) can use your .net passport in it. Personlly i believe that the interface is a hell of a lot nicer to look at anyway. Could use as a short-term solution till u get windows messenger working again.
PS. if u brought operating system retail, email or phone microsoft for support they should be able to help u out