Why won't my Divx movies play with audio in quicktime?

[kelcinicoll99]

I have a macbook pro. When i try to play my divx videos, there is video, but no audio. I've been told to download certain codecs (which i did), but they didn't seem to work. I'm technologically challenged, so i'm not sure what i'm supposed to do with these codecs once they've been downloaded, or which ones i actually need .. HELP!!