There is no official PC version of available for download. The game was released exclusively for the Xbox 360 and was never ported to Windows by its developers.
When discussing a "Highly Compressed" version of for PC, it is important to clarify that official digital downloads are quite large (usually around 8GB+). "Highly Compressed" versions (often found on third-party sites) attempt to shrink this size drastically using aggressive file compression. Forza Horizon 1 Pc Download Highly Compressed
The only legitimate way to get a "Forza Horizon 1 PC download" is to use the (an Xbox 360 emulator for Windows). Here is the step-by-step guide. There is no official PC version of available for download
Be extremely careful with sites offering ".exe" installers for Forza Horizon 1 . Because no native PC version exists, these files are often malicious software or "wrappers" that may compromise your computer's security. Be extremely careful with sites offering "
Emulating an Xbox 360 is demanding. Even though the original game only needed 2GB of RAM on console, your PC will need significantly more power to translate the code in real-time. Forza Horizon Full PC Emulation Guide | Xenia