For Windows 7, Your options:
.. Windows live mail
.. 3rd party such as thunderbird
.. Outlook (NOT outlook express). NOT FREE, unless you have one of the more expensive versions of uSoft Office
.. Last, but not least, Vista WinMail. This is the most dificault as 1) requires availability to copy vista Winmail director. Then requires porting to Windows 7. This is what I did for my wife's computer.
PS. Toms upgrade equivalant of going fom XP -> Vista