Outlook express 64 bit

The successor to Outlook Express is Windows Live Mail, which you can download from this site: http://explore.live.com/windows-live-mail

An open-source alternative is Thunderbird, available here: http://www.mozillamessaging.com/en-US/thunderbird/

I use Thunderbird and have been very happy with it.

As sminlal said.
However, if like me you are adverse to "Clound" mail and cloud apps, there are other options.

As sminlal state Thunderbird is a good option.

I need to stay with outlook (Work) so I installed Microsoft office (Freeby Office Enterprise ed) that installed the 32 Bit Outlook which works under win 7 64 Bit operating system. Office 2007 64 bit should also install a working Outlook. Outlook is just the Express with a few added features.

A 3rd option is to PORT Vista's windows mail program over to windows 7. I did that on my wife's Windows 7. To port is different than installing and requires that you have access to Vista 64 Bit. If you go this route, just google "Using Vista Windows Mail in Windows 7.