After the M (Mature 17+) rating assignment was issued for Halo 2 for Vista and just prior to the shipment of the game to retail, Microsoft notified ESRB about pertinent content found in a map editor tool that is being bundled with the game. 

The content in question, although likely to be inaccessible to the vast majority of users, displays a photograph of an individual showing his bare backside to the user when a particular error occurs, and thus warrants a ‘Partial Nudity’ content descriptor in order to alert consumers to its presence in the product. 

Microsoft has therefore applied stickers with correct ESRB rating information to the packaging of virtually all copies that will ship to retail in the U.S. and Canada.  We have been advised by Microsoft that future runs of the game will be produced without the content in question, thus negating the need for the descriptor to be displayed on those versions. 

ESRB’s job is to ensure that games are appropriately labeled, and that is precisely what we did in this case.  We greatly appreciate Microsoft’s cooperation in this matter.