All games released for Xbox 360 are required to be able to play on any console sold as an Xbox 360, by principle. The oldest functional Xbox 360 console will play the newest Xbox 360 game.
It won't be a AP2.5/XDG3 protections issue, because neither Samsung nor sub-78 Hitachi drives can do those checks. It is, however, possible that the backups have not been burned right.
As for your drive replacement, it could work... especially if the console doesn't have a factory-defined OSIG.
Use modern tools (Current version of JungleFlasher and the latest firmware pack), and follow the steps starting on pg 77 of the JungleFlasher tutorial (jftut1.4.4.pdf)
Don't spoof anything other than the key. Keep the drive version the same as whatever the new physical drive is. If games play once you're done, you're in luck! You have no defined OSIG, and any phat drive will work. If not, you're going to need a Samsung drive.
Another possibility is that the laser has gone bad, in which case you can swap the laser. Hitachi and Samsung lasers are interchangable, and it does not require any soldering.
Hope this helps!
This post has been edited by CarpeDiem0: Apr 9 2012, 10:41 AM