While you cannot download a native "full version" for PC from official sources, you can play it on PC using the . Playing Forza Horizon 1 on PC via Emulation
There is of Forza Horizon 1 . The game was released in 2012 as an Xbox 360 exclusive and has since reached "End of Life" status, meaning it has been delisted from official digital storefronts. download-forza-horizon-1-game-for-pc-free-full-version
To play the game on your computer, you must use an Xbox 360 emulator like Xenia (specifically the build is recommended for better compatibility). While you cannot download a native "full version"