If it's the Trainz configuration window that's accessible from the Trainz launcher via the 'Options' button, last night i found out how to fix this. Make sure you have your serial number in hand, and then type it into the box marked 'Serial Number'. Make sure your Caps lock is on, it will save your computer from puting that annoying FilterKeys on when you hold the 'shift' key down. Enter your serial number, then click the button marked 'Add' on the right. The serial number will then appear in the text box below it. Then click 'Ok' and select the 'Content' option in the Trainz Launcher. Trainz may have to perform a database update, but aside from that you should be good to go.