I'm suprised they manage to make this playable on modern PC. I was playing W3 Reign of Heroes a lot as youngster; but I was never able to play it again after ~2000s. The game was unplayable even at Windows XP with full W98 compatability mode.
As even Heroes3 source code was lost, which is far far more popular than W3, I never hoped that I'll ever play this game again.
Why would you play RoH over DLR?! DLR was released like two years after RoH and improved every single aspect of the game (except for graphics which were always bad in W3)!
Also the source code for Heroes 3 was not lost (you can download it right now if you know where to look). That is how the popular "Horn of the Abyss" expansion was produced and released (and the HotA guys are about to release a second new town type - The Factory- which adds to their other new town -the Cove.)