The file you are referring to, "registration code forza horizontxt" ), is a known hallmark of a common online scam
These methods involve —certainly not a simple text file. The code is validated against Microsoft’s or Valve’s servers, and the game license is permanently attached to your account. registration code forza horizontxt file size 106 kb
No malware, no 106 KB mystery files, and you support the developers. The file you are referring to, "registration code