Quicktime Pro - no audio when playing AVI files

I have a bunch of AVI files I want to play. VLC has no problem playing them, but Quicktime Pro will only show the audio, then a window will come up saying that it needs something else to play the file correctly. It then directs me to the webpage of 3rd party add-ons for Quicktime but it doesn't tell me which one I need. Any idea?

Quicktime is basically telling you that you need to install an AVI codec (the software that allows the encoding/decoding of a particular media type).

There are few options for AVI files, here is a decent place to start. Googling for AVI Quicktime OSX will also provide more options

Play AVI DivX codec Movies on Quicktime in Mac OS X Leopard | Mac OS X Leopard & Tiger Dual Boot

Thank you I'll start there. Oh and I mistyped in my original post. Quicktime will only show the video but no audio is heard.

Try installing Perian - this should solve most, if not all, codec issues you have.