quicktime

help! for some reason when i downloaded i heart huckabees and many other avi format files from friends my quicktime player will not play successfully.... sometimes it will play the whole file, with certain files the audio will not play or there will be no picture.... i have downloaded quicktime 7 for mac and have a new powerbook g4 ox

help!
e-mail me if you have any ideas... thanks so much!

hi...i have downloaded a movie from limewire and everytime i play the movie on quicktime or even windows media player i have sound but no picture...can you please help me?
yours truly
kimmy17