Sean, all games can run in Windowed mode so do not edit their
.ini files unless absolutely necessary.
As I said before, you are trying to run the game at a very high resolution. Just try to play it in Windowed mode because as you rightly said, your Windowed mode is larger than most PC users' Full Screen mode. Thanks for posting the useful information as it may be very useful should there be some similar issues in the future. Also, glad you got it fixed.
Please ask any more questions or doubts you may have.
-- Goku