As far as DOSBox games are concerned, you can go into the .conf file of each game and set the following:

[sdl]
fullresolution=0x0 (this will set DOSBox to your fullscreen resolution instead of running at the resolution needed for your scaler)

[render]
aspect=true (this will provide you with the desired black bars by upscaling the framebuffer over your desktop's full resolution)

Try this:

Start->Run

type:

rundll32.exe NvCpl.dll,dtcfg setscaling <display#> [<NV device moniker>] <mode: 0,1, 2, 3, 5>

where the scaling modes are defined as follows:
• 0: Default
• 1: Native
• 2: Scaled
• 3: Centered
• 5: Aspect scaling (for wide panel LCD)

So in your case since you want aspect ratio scaling and have only one display, you'd go:

rundll32.exe NvCpl.dll,dtcfg setscaling 1 DA 5

No. aspect=true in Dosbox only makes sure that modes with non-square pixels (e.g. 320x200 VGA mode) get the correct 4:3 ratio. These modes were very popular in most DOS games of the early 90s era, when CRT monitor could stretch the pixels to the correct ratio. It's no longer possible with LCD monitors which have pixels of a fixed square sides.
Basically it simply changes a 320x200 resolution into 320x240.
Anyway, it has nothing to do with the black bars, and the scaling when in full screen mode.

Yep, I didn't read the entire thread. My bad.

I have a similar setup on my laptop, an 'Optimus" system (integrated for general use, dedicated for programs that need it) and I believe that the Intel is treated as the primary graphics card, which is why certain options are missing for Nvidia, because Intel handles them.

I have a couple of suggestions for possible fixes.

1) If you have your Intel options set to display in the notifications area (bottom right, next to the clock), you should be able to right click > Graphics Options > Panel Fit > Maintain Display Scaling.

2) Right click the desktop > "Graphics Properties..." and "Graphics Options" both show for me, and might for you, you can then select the latter and go Panel Fit > Maintain Display Scaling from there as well.

Tell me if any of that works for you.

Go to your Nvidia control panel, and click on Adjust Desktop Size and position
Select Aspect Ratio for Scaling mode
Click the drop down menu under Perform scaling on:
Select GPU.
Check the box Override the scaling mode set by games and programs.
????
Profit

My reason being the same as the one for not using any mods in the first place. I just like the vanilla experience. If I'm playing a "classic" game for the first time, enhancing it via mods would deprive me of the chance to experience the game as it was back then and judge it for what it originally was. I don't expect everybody to agree with me on that or even understand my position, but it's how I roll. Again, using a widescreen fix for a game that can't be properly rendered in 4:3 is a possibility I'm willing to consider, as is checking out what mods there are for a game I'm replaying. Anyway... see below.

Thanks anyway for the good intentions, Hickory.

1) Checked it, tried every option I could try, nothing seemed to make a difference.
2) Good idea, but nope, it was set as 60 Hz, as it should (it's the only option I get at 1920x1080, btw).

Good to know my laptop's not all that weird. Can't help finding the nVidia control panel creepily empty whenever I need to do anything there, though.

Duly noted.

That sounds like something worth trying, but... see below.

You never go to bed without learning something new.

So... Thanks everybody for your suggestions. Your support was much appreciated in these dark times. The whole point has been rendered moot, though, because the motherf$cker seems to have fixed itself. Yeah, that's right. I went too grab some dinner, turned on the computer in order to reply to the thread and let you know that our efforts so far hadn't succeeded... and there it was, working perfectly, as if it hadn't driven me to near-madness for the best part of a week. I guess I probably look like a fool now, but I'm a happy fool. A happy fool that is yet anxious about the possibility of this crap just happening again at any point in the future, whenever I expect it the least. But hey, I'll take what I can get.

So thanks again, and I'll mark SCPM's post as the solution, since he had me learn something cool about DOSBox (before some other folks had me learn some other cool stuff). May the Light guide us all, and long live GOG and its glorious community.

Addendum for those that posted while I was writing this long-winded closing post:

1) Nope, I didn't have it, but I've activated it now. You see, the Spanish translation for the Intel control panel is so godawful, I just don't activate some otherwise useful features because I just cannot understand what they are. I'll take decent English over broken Spanish any time of the day. Hell, I'll take decent Japanese over broken Spanish any time of the day.

2) The option you mention was set all the way, it's the only option I can get on a 1920x1080 resolution.

I must have created a very boring thread, because nobody seems to be reading all of it XD. Thanks anyway for trying to help, and for the chuckle-inducing South Park reference.

Oh well, I was actually hoping this gets tested on your laptop. I use this method on my old Windows XP machine that has an "creepily empty" nVidia control panel that too just refuses to show the tab where Aspect Ratio can be changed. I was curious if this works on newer Windows too.

You wouldn't want to try it by any chance...?

Anyway, I'm happy it worked.

Mate, I'm not touching any graphic settings on my laptop for a while. Not with a ten foot pole, not for a million gil. But I'll be sure to keep this thread favourited in case I ever need it again (I so hope I never need it again, lest I lose what little sanity I've got left). If there are any volunteers around, though, it definitely seems legit :-P.

hehe, I understand.

I found this in the manual:
developer.download.nvidia.com/SDK/9.5/Samples/DEMOS/common/src/NvCpl/docs/NVControlPanel_API.pdf
(it's on top of page 17, that's p.23 of the pdf file)

In any case, it's not really all that important, but if anyone is looking to do a good deed for the day, you can test this out if you have a 64 bit Windows OS and let me know if this still works.

That's great, thanks for the info! So you can adjust scaling through the Intel settings when you have a dedicating card as well using Optimus technology to switch between the two of them?

Apparently, yes. But again, I must suck at my own native language, because I can hardly understand the Spanish Intel control panel. In 1920x1080, though, there's only one scaling option available. As for switching, my laptop chooses automatically between the two according to its own balance of performance and efficiency, but you can override its choice and set a specific program to always use the Intel or the nVidia according to your own needs.

Just want to say thank you! Been fighting the missing GPU scaling options under Windows XP with a 630 GT. At some point the drivers just seem to not show this option any more under XP.

with your trick I was able to set it to "aspect ratio" scaling which is what I was after :D