How can I open and play an avi file with Windows Media Player or Quick Time

How can I open and play an .AVI file with Windows Media Player or Quick Time?

I downloaded a video, that is in the avi format and neither my windows media player nor my quicktime will open and play it. How can I? Do I need to change the format, if so how do I do that?

Install K-Lite Mega Codec Pack and you will be able to watch most videos with your Windows Media Player.

Alternatively you can download freeware VLC player that comes with most codecs you will ever need.