Verified answer

You go to the store and buy the hard drive. Then you put the hard drive in your 360, then go to XBL and download the latest update. Then you need to go here to see if the XBX game is playable on the 360:

http://www.xbox.com/en-US/games/backwardcompatibil...

You need the hard drive to even have a chance of playing XBX games.

you'll have to buy a memory card and have the 360 connected to the Internet so it can download the need requirements to play backwards compatible games.

note: not all xbox games can be played on the 360