Error Code 6 is simply that it cannot unlock your hdd on xbox 2, so you prolly
locked it in the first xbox, where the eeprom (the key's etc) are different.
You require to put that hdd back in xbox #1, use config magic or evox to unlock
it, and then put it back in xbox#2, after that you can lock it in xbox #2, so you
have it locked with the right key , which is your problem here buddy ;-)