on a second look, it appears to be the same stuff as my macbook
cool 😱 so it looks very likely we should be-able just to copy the Divx, etc codecs in there and it should them be-able to play avi's, could you try ?
but first you'll need to make the AVI file iTunes friendly. open a AVI in quicktime the do a save as -> choese self contained file. this will then make the AVI file with a quicktime wrapper around it (a .MOV file) then import that file into iTunes then sync it to the AppleTV