.DM_83 files are recordings of a game played in 'Return to Castle Wolfenstein: Enemy Territory (v. 1.02)', which is a first-person three dimensional action game. .DM_83 files record the gameplay of any mission and can allow for play back later using the program's "Replays" option. .DM_83 files only apply to specific versions of the game, while earlier versions of 'Wolfenstein: Enemy Territory' store these files as .DM_82 files, while later versions save recordings with a .DM_84 extension.