It always swich to 1920x1080i,
"Change compatibility settings for nwnmain.exe - Windows XP" not work
"Disable display scaling on high DPI settings" not work
"Nvidia Control Panel scaling on GPU" not work
My video card is Nvidia 750ti
I was in the middle of typing this big reply about how I'd searched everywhere for a solution to this, and how I'd found a thread that linked to an NVidia Forum thread that solved this problem for Crysis 1, Warhead, and 2. I was about to point out that the thread was unhelpful because it relied on expired image links to fully illustrate the solution, but I went back into NWN just now to look at the resolution I was playing at (1680x1050) and noticed that the custom resolution I'd created (1916x1080@60hz) while trying to follow the aforementioned externally-linked steps was in the game's resolution list. I applied that resolution and am overjoyed to see that it works flawlessly. Can't even tell those 4 pixels are missing from the full resolution, and it runs at full refresh rate!
Open your Nvidia Control Panel and go to Change Resolution under Display. Scroll down below the list of resolutions, click the Customize button, then Create Custom Resolution. Manually enter the resolution of 1916 Horizontal and 1080 Vertical, making sure the Refresh rate is 60, Color Depth is 32, and Scan Type is Progressive. Test it and say yes to save the resolution. Then when you launch the game, set 1916x1080 60Hz as your resolution. Problem solved, completely by accident!