[Agrajag]

What are you talking about? Heroes 3 did not have an option to remove items from the game.
You had to open the map editor, locate the relevant map, go into the correct settings panel and then find and disable the items, then rename the map to prevent confusion and then resave it in another name in the correct location.

Unless you are talking about WoG (which IIRC allows you to disable whatever item you want from the game settings menu), but then again, that's an independant mod for the game, and we are assuming we are dealing with people that can't install mods...