when you connect your usb drive to the console the files are looking with the game icon? i mean they are not corrupted? if yes you are done with disc 1
yes the disc 1 content can be placed into a usb drive formatted with xbox, extract the disc 1 files with "XBOX360 ISO Extract" you will find files i don't know their names its about 5.6GB without extension in a folder with lot of numbers (sorry i don't have the game to tell you directly the path!) then select and drag those files into horizon ( first connect your usb drive which is formatted with xbox ) and wait until its done then connect your drive to your console and if you want you can copy them to the xbox's HDD
I have done this but getting same error as jokerbow mentioned above. 1. Used Xbox Backup Creator to extract 4 files 2. Used Horizon to inject them to usb drive one by one (For some reason if I put all 4 files at same time, xbox 360 will detect one of them and show other 3 as corrupted with yellow sign) 3. Moved 4 files to xbox 360 internal drive 4. Installed Disc 2 from burned disc When I run game it still asks to insert Disc 1 to install files, even though all 4 files are already there. Any solution to this?