If you have trouble running Homm 4 smoothly on the newest systems, right click the game executable and go to properties. Under the compatibility tab, click on reduced color mode and set color to 16 bits.
If you game crashes during battle, go into the task manager, right click your game executable process, and click set affinity. Select only one CPU core to run the game. Very occasionally the game still crashes during battle, but it’s much more often then if you don’t do this step.