I want to download coldfusion 7 ?

Umm, why? In my experience I found no compatibility issues between 7 and 9. I would seriously consider installing 10 if I were you, but 9 as the earliest version to install.

Adobe no longer supports ColdFusion 7 (the End-of-Extended-Support was 2/7/12), so I wouldn't expect to find a download on their site.  If you still have a valid license key for CF7, you might either contact Adobe Support directly to see if they can make a download accessible to you, or post a message on the House Of Fusion CF-Talk list and see if a kind soul might have a copy of the installer they can get to you.

-Carl V.