Older versions of the game (from the 90s) rarely run on modern Windows without a DOS emulator like DOSBox or specific community patches. Key Game Features If you are looking for info on why this edition is special:

You can often find the original demo versions of the game for free on archive sites. These include a limited number of unique missions not found in the main game.

Technically, there is no official "free" full version. However, there are a few nuances: