The file I got was an ISO inside a RAR and I just extracted it to a DVD. The DVD wouldn't autostart so I just executed setup.exe on the dvd.
My Vista was corrupted when I tried to install a wireless driver so i did a clean install of Vista and installed my apps and i had to do updates up to Vista SP1 in order to upgrade to Winodws 7. Well I did an upgrade from Vista Ultimate to build 6801 and then an upgrade to build 7000. What the upgrade does is takes your Vista setup and moves it in to a folder called Windows.old which it uses if it has to do a restore to previous version.
To the best of my knowledge there is no way to do what you are wanting to do. The windows.old folder is the archive where it stores the windows, program files, and users folders. The program files folder will not work because it has been moved and any registry entries that have been made will have to get changed. So no i do not think it is possible. what I suggest is to dual-boot both VISTA and Windows 7 that way if you need to run an application you can always go back to VISTA