Have you just tried one or several, don't know how you're trying to open them but I just double click and you'll then see several files, keep dilling down if you need to so there's no more folders then copy everything in there and then paste it into, C Drive, Program files, FMS, Models.
I assume you signed up with a username etc although from memory I don't think lets you dowmload anything until you have.

Actually I've just re-read what you actually wrote, are you sure you've registered properly and the logged in - that's all I can think of as I've never had a problem ?????????