.cpn this is a campaign file, place it in the "data" folder
.cpx this is a campaign made for TT, place it in the "data" folder
.lgt this is a custom light for scenarios or rms, for example "night" "sunset", place it in the data folder
.dcl this is a model (par of a mod), it goes to the "model" folder
.brg the same, it goes to model folder
.sav it is a save for the game, place it in the "savegame" folder
.wav a sound file, place it in the "sound" folder
.mp3 a sound file, place it in the "sound" folder
.ddt it is a texture, usually for a unit, place it in the "textures" folder
.bti ^ the same, place it in the "textures" folder
.tga this is an image for a rm, place it in the "ui" folder of "textures" folder
.btx the same, place it in the "ui" folder of "textures" folder
.bdt the same, place it in the "ui" folder of "textures" folder
THIS CAME FROM HERE http://aom.heavengames.com/cgi-bin/forums/display.cgi?action=ct&f=13,15797,0,30