Windows 7 doesn't have a pre-installed email client.
But its very easy to download Windows Live Mail, part of the Windows Live Essentials
Live Essentials also gives you Live Messenger, Photo Gallery, Movie Maker, Writer, Toolbar, Family Safety. Everything is optional, you can install just Live Mail of the rest of what you might want.
Once you have Live Mail installed, setup TalkTalk email as you would in Outlook Express. TalkTalk Email Settings