I recently purchased a used 360 from ebay. Its the black s model with 250 gb hd. Some games that I play in it give me an incorrect region code. Other games play just like they are suppose to. All games are NTSC games. The guy that I bought it from says that he has played lots of Call of Duty and Halo games with discs bought from Gamestop without any problems. I have chatted with xbox 360 support for hours and they dont know what the problem is. I would appreciate any help that I can get in regards to this matter.