I haven't been succesful testing iTunes for paramount; if you know of a way I'd love to learn it!
I have a little trick for checking iTunes codes. This works for movies that don't need xmls. What I do is input the code into iTunes, and click Redeem. When it asks if I want to download the movie now or later, I force quit iTunes without picking either option (on my Mac, I go to the apple menu and go to "force quit"... on Windows, I assume you could do the same through the task manager and end the iTunes process, but I haven't tested it in Windows).
I've only done this method a few times so far, because I just figured it out recently. I'd love to know if anyone else has success with it.