Thanks to Xbox 360 backwards compatibility, it’s possible to play all of the best games from the original Xbox on the newer system. If your Xbox games aren’t playing on your Xbox 360, it could be that your hard drive is missing important files that enable backwards compatibility.
Revisiting Original Xbox Backwards Compatibility on Xbox 360 – Play ALL Original Xbox Games | MVG
The Xbox 360 hard drive uses a special partition to run Xbox games. Xbox 360 compatibility issues usually occur when replacing the Xbox 360 hard drive. If you purchased your console used or refurbished, the hard drive may have been swapped out before you purchased it. This is a common issue reported by players buying from eBay.
In order to make more money, some eBay sellers are buying consoles with official 20GB Microsoft hard drives for next to nothing and replacing them with larger laptop hard drives. This way, they can then sell them for less than an official drive of the same size and still make a profit. While these hacked hard drives function exactly the same as an official drive, most are missing the partition needed to run Xbox games.
Original Xbox games will work on the Xbox 360 Slim and other models, with one exception: the 4GB version of the 360 Slim is not backwards compatible. The 4GB Slim doesn’t actually have a hard drive, so you’ll need to install one with the proper partition in order to play original Xbox titles.
