There are no reputable repackers (groups known for legitimate compression, like FitGirl or DODI) that work on Xbox 360 ROMs for PC. The entire ecosystem of "Highly Compressed FH1" is a fabrication built on the ignorance of the userbase regarding emulation.
If you encounter a site offering a direct download for "Forza Horizon 1 PC," be cautious for the following reasons:
Forza Horizon 1 Pc Download Extra Quality Highly Compressed HOT! - Google Drive. Google Docs Forza Horizon REMASTERED on Xenia Emulator
Downloading highly compressed versions of Forza Horizon 1 PC can have significant risks and implications: