HoMM3 HD is a mod (add-on) for the game Heroes of Might and Magic 3.

R55Max,
It's hard to understand what you wrote; basically, nothing is clear.


So, it only runs in windowed mode? And what happens when you press F4?

And what is it like now? How was it before?

So, even if you set 1280x800 (the physical resolution of your screen), the game still runs at 1024x768? If this is really the case, it's the most unbelievable thing you've described.

So, when you set, say, 800x600 (aspect ratio: 4:3) or 1024x768 (4:3),
the resolution is set while maintaining the aspect ratio, but you want it to be stretched to 8:5? Well, many modern monitors and graphics cards allow you to adjust how a resolution that doesn't match the monitor's aspect ratio is displayed. And if your 800x600 resolution used to be stretched to fill the screen, but now it's displayed with black bars, it's obvious that your laptop has this functionality. So, instead of uselessly reinstalling the game and the HD mod, you should look into the display settings on your laptop (either a special proprietary utility or just the graphics card settings).
As a last resort, you can try reinstalling the video drivers.

In general, there's no need to panic, and the HD mod isn't the problem. The HD mod simply sends a command to DirectX to set a specific resolution (from the system's supported resolutions), and then it's completely unrelated to the HD mod how DirectX handles this command, how it passes it to the graphics card, and how the graphics card ultimately reacts to it.

You understood everything correctly, and the most unbelievable things are actually quite possible.
Now, about what you didn't understand:
"As it is now" means how it is after the MOD. I described how it is. I'll explain it again and break it down: I was playing the game normally. The game was in 800*600 resolution, but it filled the entire screen of my laptop (how to put it... it's like this resolution can somehow fill the entire screen).
After installing the MOD, I set the resolution to 1024*768, and it changed to that, but it only occupied the physical pixels on the monitor with my physical 1280*800, and the rest of the pixels were just black. When I changed the resolution to less than 1024*768, the resolution changes corresponded to their physical number of pixels, and the rest of the monitor background remained black. On the other hand, if I set any resolution greater than 1024*768, the resolution on the monitor still remained the same and equal to 1024*768 physical pixels.

When I pressed F4, a normal windowed mode of the game was displayed with the desktop visible and no empty pixels in the window.

As for the MOD, I have nothing against it, but since its installation and changing the resolution parameters in this way provoke such reactions from my hardware, it can no longer be claimed that the MOD has no effect. I'm not arguing that I should look for possible settings on my system. If I knew where and what to change, I probably wouldn't be asking. It's just that we need to figure out where to look for possible problems, why, for example, my specific graphics card behaves this way when your MOD is installed.

In general, reinstalling Windows solved the problem, which I didn't want to do. But reinstalling the MOD gave the same sad result. I can do without the MOD, but I'm just curious why this happens, if you say that the MOD shouldn't have any effect...