I am also having problems with avi files and there is no sound and I got this message “The audio codec identified by the format tag 1 is required to play this file. To determine if this codec is available to download from the Web, click Web Help” i played them on my old computer with an older version of windows media player and it worked so i think this is a problem on 9 series. but i couldn’t uninstall it even by deleting all files there is no uninstall icon in order to instal 7.1