I wanted to run Windows 7 on a Macbook Pro using Parallels and the Yosemite OS. I received the Windows 7 product key in the post after a few days. I had some difficulty understanding quite what I was supposed to do with it, but the support staff at Techee were wonderfully helpful. With their patient guidance I downloaded the ISO file (a disk image file) from a link they provided on their website and opened it on the Mac using the DiskUtility. I didn't even have to burn it to a CD (which can be a bit tricky). I then did a clean install with Parallels, using the product key and hey presto, it works! I haven't figured out yet how to transfer files from my old XP system, but I'll get there.