I was playing Call of Duty 4 Modern Warfare "free for all" on XBox Live "multiplayer". Suddenly everyone began to fly in the air...I continued to play (I now know that was a mistake). The game ended, my stats were reduced from a 5 star general to a private. I am now blocked from all Call of Duty 4 Modern Warfare on line games since the only way to access any of the on line games is to promote to private first class. I can't promote because the games are blocked. So...my question is: how do I delete my current gamer tag and create a new one that will allow to me once again play the game on line??