I have a really weird problem which I don't really know how to describe, so please bear with me.

I'm playing on an Acer Aspire notebook (running Windows 7 Ultimate 64-bit) with a native screen resolution of 1366x768. When I select 1024x768 resolution in NWN, the screen looks like it should, i.e. like this (images hosted on imgur.com because they're too big for upload); the black borders left and right are normal for a game running with a 4:3 resolution on a widescreen display.

However, when I select 800x600 resolution, the screen looks like this. The actual screen resolution stays the same, i.e. 1366x768, and only the portion of the screen used by the game gets changed to 800x600, which results in black borders at the top and bottom.

I would very much like to play NWN in 800x600. Not only because it is (or at least was upon release) the default resolution and is the one I'm most comfortable with, but also because it puts far less strain on my poor, old hardware.

So far I've tried changing the resolution via the in-game options, the configuration tool (nwconfig.exe), and by editing nwn.ini directly. The changes stick, but the results don't change. And on a related note, I also can't play in windowed mode, which I think is another symptom of this weird problem.

Your problem is a scaling problem that needs to be fixed in your graphics card control panel. You need to find where scaling is controlled and set it to override the game and scale to aspect and desktop resolution -- I have no idea where this would be in an Acer Aspire, sorry.

I'm certainly going to give that a try, thanks. Still, I wonder why other games that change resolution (original Baldur's Gate and Icewind Dale, Red Faction, Deus Ex, etc.) work flawlessly and only NWN has that problem.

Baldur's Gate, Icewind Dale etc. were designed around DirectX, whereas NWN has it's own proprietary (read 'hacky') version of OpenGL driving things. Maybe that's it. But regardless, your GPU should ideally be told to control scaling.

I've spend the last 20 minutes going through the NVIDIA Control Panel, but I couldn't find anything related to scaling -- I can post screenshots of it in case that helps. I did create a Programs Settings entry under "Manage 3D Settings" for NWN and set everything to application-controlled that I could, but to no avail.

This is really confusing for me because I could play the original retail version of NWN along with both expansions in 800x600 just fine on this very same notebook a few years ago.

It's under Display Adjust desktop size and position
Perform scaling on GPU

Thank you, found it. Anyways, GPU is the only option for "Perform scaling on". As for scaling mode, I've tried each of the three settings (see screenshot), each with and without "Override the scaling mode...". Still no effect, sadly.

I went back and tried again, and you're right -- I must have missed one of the combinations. "Aspect ratio" plus "Override the scaling mode..." did the trick. For some reason the screen is a tad blurry now, but it's not so bad that I can't read the text anymore.

Thank you!

Under " Perform Scaling On"... I do not have the " Override Scaling Mode option"

I have the AMD Catalyst Control Center version 2015.0804.21.41908

Yeah, I had the same problem and AMD doesn't have that option.
Turns out though, my monitor has Display Mode setting which could be set to maintain aspect ratio, stretch and the other stuff.
So now playing lower resolution at full screen.