Windows 7 has the folder for windows mail, However they disabled it.
The current options are:
1) download windows live mail
2) Get a 3rd party program such as Mozilla Thunderbird
3) Buy Outlook. Outlook is included in the higher end versions of uSoft office.
4) Harder to do, port vista winmail over to windows 7. (I did this for my wife as she liked the Vista winmail program.
From what I've heard you can not use Outlook exspress (which came with XP)