Outlook Express does not exist. You can not use it. It's as simple as that. You do have a few options though. The one Microsoft would have you go with would be Windows Live Mail. http://download.live.com/wlmail
Where can I go to download a 64 bit version of Outlook Express for Windows 7?
Outlook Express is not included with Windows 7. Instead you have the option of using Windows Live Mail. To learn more about the features of Windows Live Mail, please see the following link: http://download.live.com/wlmail