I meant the setup programme. That's interesting, because my list doesn't show 1600x900, 1280x720, both of which I use regularly and are in the list of resolutions I can choose for Windows. They're also also available when I play other games.
As far as I can tell, there aren't any 16:9 resolutions in the setup list, apart from 1920x1080. (1360x768 is there, but it's not quite 16:9).
I can create a 1280x720 game, and set it to run at 'game resolution'. This runs 1280x720 successfully, however when I run setup again, it defaults back to 'desktop resolution'.