there are two ways around this, i'm not sure of the legality of either, but you won't here about these in forums.
1) download a vista64 iso via a torrent. since vista64 doesn't require a key to install, you'll be able to make a boot disc, install vista-64 and then unpack your win7 install files and create a bootable iso. repeat process for win7 and voila
2) install win7 64bit RC to extract files and rinse and repeat.
I'm assuming you're talking about the student files that you got as a download. Everyone was expecting iso files and instead everyone got a bunch of files that won't allow you to extract in a 32-bit environment. (you can do this install via a vmware virtual server too to make your life easier if you have the space
ms and digital river didn't really think that one through too well.