Hello community, since I have a widescreen monitor I noticed that HOMM I and HOMM II only run in a small dos box window. Its size is about 1/10 of my monitor so I wonder if it is possible to run them like HOMM III, which has black bars left and right from the game but this is OK and the game runs pretty good. Any one has same problems or knows about a solution? Would be very happy. Cheers!

Currently I'm using HOMM2 on Linux using a Dell 24' monitor with a resolution of 1920x1080 and it fills the entire screen. In order for us to help you, we're going to need to know what Operating System you're using, what version you have and what, if any, updates you've installed. As examples, you might be running Windows 10, or Fedora Linux 41, fully up to date on patches. If you don't understand this, or are uncertain how to find out the answers, just respond with what you do know and somebody here will know what you need to do to get more details.

OS doesn't matter if you use the DOS version.
You need to edit one of the DOSBox .CONF files, so that the relevant lines are something like this:

fullscreen=true
fulldouble=false
fullresolution=desktop
windowresolution=original
output=Overlay

[render]
aspect=true
scaler=normal2x