You can edit one XML file that is somewere in your PC

, but all setting in it can also be changed using the game menu, there is no "hidden" feature (
until now).
I managed to play windowed using one tool named D3DLookingGlass, you can find it using google. But it don't look good, there is no real "window", the game just become stuck in up-left corner of the screen, at last you can switch to your MSN, Broswer, etc, faster than if in fullscreen.