Ok say I have MW3 disk (original) that is badly scratched and when I try to play I always get an error. (please clean disk error). and when you install a certain game you can see it in your hardrive . Can I download this installation from the internet and put it in my xbox through horizon for example?
No that won't work sorry, it needs to be signed by the Xbox that the disc is installing too, it wouldn't even work if you used a legit copy on another Xbox with your HDD, it needs to be the same Xbox your HDD is on when the game is installing.