As already stated:
(1) Windows Live mail
(2) 3rd party program such as Thunderbired (Others exit, just googe email program)
(3) Outlook - NOT OUTLOOK EXPRESS. Costly unless you have one of the upper end Microsoft Office pakages that includes outlook.
(4) Most difficult - Copy Vista Winmail over to the windows 7 OS. This is what I did for wife's computer as she liked Vista winmail. As I indicated it is more involved as it is not just a "copy" as you have to change "privelage" (can google using vista winmail in Windows 7).