am a bit new to all this and for most of the movies i try to download on plyback the sound is there but the image is covered by a green screen. the file is playing in patches in the background but the majority of the screen is just blank. the images are obviously downloading but they look encrypted maybe? think it may just be for avi files but am not sure. have downloaded divx converter and think i have codecs.
please help with any ideas.

Maybe try VLC media player it has built in codecs and plays just about all files, its a free download.

Hope this helps