Parallels 5 and Windows 7 Download

I've tried with no success to install Windows 7, using download files from MS (no ISO image files), into Parallels 5 on new iMac. Is this not possible to do? Do I need to purchase Windows 7 on disk?

 

You can always redownload the .iso (check download options) from the Microsoft store and burn a DVD, there is also a way to burn the disc from the files you downloaded; no need to repurchase at any rate.