Neverwinter Nights works on 16:9 using 856x480p and 1920x1080i. At intermediate resolutions (960, etc) the screen scrolls up and down as windows desktop does. Apparently the game doesn't lock the resolution.
To get widescreen working, one needs to edit
X:\NeverwinterNights\NWN\nwn.ini like this:
[Display Options]
Width=856
Height=480
BitsPerPixels=32
RefreshRate=60
SafeMovie=1
[Video Options]
Enable VSync=1
RefreshRate must be set to whatever one uses in Powerstrip, normally 60 (I'm using ATI's HDTV adapter).
The SafeMovie option is important, because without it, in-game movies don't work (you end up with a blank screen while audio plays).
Notes: The intro movies do not play in widescreen, but the rest of the game works fine. I recommend using 856 rather than 1920, and relying on 4x antialiasing to improve the image quality. There is no noticeable stretching in 16:9 widescreen.
Note: One or more widescreen video clips and/or screenshots of this title are available in our LIBRARY.