ok,

I bought a flashed xbox 360, you know the ones that you can play your "back up" games on

I made the mistake of doing the firmware auto update and ofcourse now can't play any of my "back up" copies.

So has my 360 now turned just like the original unmodded 360?? If I play an original game online, will I get 360 slapped and banned?

Not sure but you can try hehehe