Try hitting next without typing in anything. if that works, it'll put Windows on in evaluation mode, where when it prompts you, or you click "Activate Now" in system properties, you'll need to be connected to the internet and provide the product key than.
Toss a few bucks thier way and I'm sure they'd be more than happy to assist. We'd have the install.wim in our file, but than MS might come after us...
Better to be legal than sorry.