The Heroes3HDSetup.exe utility, after clicking "Apply and Launch" or "Ok," writes the selected resolution to the HiRez.ini file. I suspect that, for some reason, the HiRez.ini file is marked as read-only or is being used by another process. In this case, the utility won't provide any feedback or modify the .ini file. My mistake. I will fix this in the next version. However, I absolutely don't believe that it selectively records 1024x767 but not 1025x768.
In general, the visual examples helped, and we managed to solve the problem:), especially since we have the same software on our laptops.
I also needed to sort out the drivers.
Excellent mod ;)