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

baratorch, thank you for your efforts! Probably, this is because:

the game is not linked to the registry and writes to the _HD3_.ini file (and reads from it) instead.

Upon the first launch of HD 3.0 RC8 and Final, the general game settings and battle settings are reset. After that, they remain as selected.