If the video uses a proprietary or customized codec, you may need to install. 7 Pro for the OS and the codec for the.avi videos is codec imm4.
Try Perian from http://perian.org/
You should read this support page http://perian.org/#support in case you need to delete older codecs. In Macintosh HD/Library/Quicktime/ delete any files relating to DivX (Perian already has them), particularly any DivX extension to Safari. However it should be noted that Perian is not an internet plugin and will not play DivX files imbedded on a website. For that you will need the DivX Player browser plugin available from http://www.divx.com/en/software/mac
Note that Perian will be discontinued after the release of Mountain Lion:
http://reviews.cnet.com/8301-13727_7-57434082-263/perian-plug-in-for-quicktime-t o-be-discontinued/?tag=txt;title
Note that Perian will be discontinued after the release of Mountain Lion:
http://reviews.cnet.com/8301-13727_7-57434082-263/perian-plug-in-for-quicktime-t o-be-discontinued/?tag=txt;title
Jun 13, 2012 2:10 AM