How to play .avi files in quicktime

first want you need is:
Quicktime
3ivx- d4 4.5.1
Divx Bundle- 6.0 pro
Ac3filter- 1.0.2

you will play .avi in quicktime..

Yup, you need to install right CODEC first.
http://www.free-codecs.com/download/Codec_Pack_All_in_1.htm

Or, convert your AVI video to QuickTime video with Mac video converter.

WMV Video Converter for mac, DVD to WMV Ripper.