Windows 7 does not come with an email program out-of-the-box.
If you've installed a professional level of Microsoft Office that includes Outlook (that's Outlook not Outlook Express), then you can use that comprehensive email/calendaring program.
Otherwise, download Windows Live Mail: http://explore.live.com/windows-live-mail
There are quite a number of non-Microsoft solutions for email: Pegasus, Eudora etc. etc.:
[Top 12 Free Email Programs for Windows]http://email.about.com/od/windowsemailclients/tp/free_email_prog.htm
'Hope this helps,