Hi there & Welcome to Tom's Hardware!
Windows 7 does not have a built in email program (client) the way win-XP had outlook express.
You need to install your own favorite email program, or could download Windows Live Mail, use Outlook either as a separate install or as part of Ofice, or use one of the many Web based email programs available. Your ISP has a webmail program you can use, there's also Hotmail, or G-mail, or Yahoo mail, or even Yahoo's Y-Mail.
Lot's of choices, just not one already there to click on.