Hi!
I hear music when I open a game, but the image is black. Does anyone know how to fix it?

Try this:

https://www.gog.com/forum/heroes_of_might_and_magic_series/graphic_gl_wrapper_for_all_heroes_heroes_of_might_and_magic_1_2_3_4_and_chronicles_for_better_wo

Thx, but this thread is huge and link from the beginning is not working. I'll try to find something there tomorrow.

Alternatively first try to reset setting deleting this registry and maybe files in saves folder (look to GameData section in this article)
http://www.pcgamingwiki.com/wiki/Heroes_of_Might_and_Magic_IV

Is it running on your graphics card? With my laptop, I think I had to change to use integrated graphics, but can't really remember. You can right click the exe and try selecting the graphics processor to use when running.