With windows, it will automatically default to the windows install wizard, no installer really needs to be selected so that isn't it. I can't really see your downloading it for him as a problem unless there's some sort of format that gets changed by being on a Mac system, but I don't believe that would be the case, it should still work just fine. You could have him download it directly, which would solve the problem if it was something to do with Windows formatting vs Mac formatting, and if that's not the problem, sometimes a download gets corrupted, so him downloading it directly would solve either problem. The only suggestion I've got is to have him download it himself and see if it works then.