If you don't mind playing in windowed mode it's possible. If you press ALT + RETURN in game you will enter windowed mode, but by then the screen resolution will already have changed. There is a way to activate that mode as the default by editing nwn.ini:
[Display Options]
FullScreen=0
AllowWindowedMode=1
If FullScreen is 0 you will get windowed mode otherwise full screen mode.