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

Pradromalo, thank you. Does this only happen in [32-bit] mode, or also in [automatic 16-bit] and [standard]?

Medium_HP, I downloaded [Geedunk] (820MB archive, 883MB after extraction) - it's the same as the GoG Complete, and HD works fine for me with it, so I can't say what the problem is and how to fix it...