Since a PC download is not possible, the only verified ways to play the original Forza Horizon are:

Here is the secret that many "PC download" hunters miss: You don't need to emulate or pirate. You can play Forza Horizon 1 on your PC via .

Released only for Xbox 360. It is playable on Xbox One and Xbox Series X/S via backwards compatibility if you own a physical disc or previously purchased it digitally.