A legitimate (but not downloadable) method to play FH2 on a Windows 10 PC in 2021 is or Xbox Cloud Gaming (Beta) . You need:
Below is a summary of the current state of playing Forza Horizon 2 on PC as of 2021 and beyond. Can You Play Forza Horizon 2 on PC? forza horizon 2 pc download windows 10 2021
If you want the Forza experience without the headache of emulation, these titles are natively optimized for PC: A legitimate (but not downloadable) method to play
You must use the Xbox 360 version of the game, not the Xbox One version, as there is currently no functional Xbox One emulator. not the Xbox One version