A Forza Horizon 1 PC registration code is a unique 25-character code that comes with your game purchase. It's used to activate your game on the Microsoft Store, allowing you to access the full game and its features. Without a valid registration code, you won't be able to play the game.

If you've purchased a physical copy of the game, the registration code can be found on the game's packaging or on a separate card.

If you've purchased Forza Horizon 1 on PC through the Microsoft Store, your registration code can be found in your email inbox. Look for an email from Microsoft with the subject "Your Forza Horizon 1 purchase" or "Microsoft Store: Forza Horizon 1". The email will contain your registration code.