Windows 7 did include a email program (it on your computer) but thanks to the antitrust lawsuits they opted to disable it.
.. As nikorr suggested - windows live mail
.. Download a 3rd party email client. There are several. Just google windows 7 email program. Such as Mozillia's firefox. I have both that and Outlook on my work laptop.
.. If you own a higher end MS office suite, you can install OUTlook (It is not outlook express). Too expensive to buy.
.. The hardest option, which I had to do for my wifes computer, Port vista winmail program. This requires access to a Vista machine and knowlege about setting "permissions". Not the easiest, but works.