Hello, I am posting for a friend
From what she told she's experiencing a problem with avi files. She can't get them to play neither in Ares nor in Windows Media player. So I told that it might not be a problem of the two programs listed above but a problem in the settings. Please help me to help her!
Thanks so much

You probably need to install the necessary codecs, or use a media player with built-in codecs such as VLC. A popular codec that supports many formats is FFdshow.

I'll second VLC.

You can get it here: VLC media player - Overview

Thank you so much for your help

I use divx player, works fine