The most important fact to clear up is this: It was an Xbox 360 exclusive.
The most popular choice is Xenia , specifically the Xenia Canary build, which supports patches for better performance. download forza horizon 1 pc free extra quality
The most secure method is to own the physical disc and "dump" the ISO file yourself. The most important fact to clear up is
“Forza Horizon 1 was a masterpiece lost to console exclusivity. This version runs via a custom-built Xenia emulator wrapper optimized for x64 architecture. The 'Extra Quality' setting unlocks 4K textures and removes the 30FPS cap. Enjoy Colorado the way it was meant to be seen.” specifically the Xenia Canary build