my computer wont let me put avi files on my windows moviemaker, is there a certain program I need to download to be able to play avi files?

Well, DivX can play avi files, and maybe VLC player can too, I'm not too sure about VLC but DivX can definitely play avi files.

if you have Ahead Nero it will play avi

If you're looking to place DivX .avi files into Windows Movie Maker, you need a DivX codec: sure VLC and Nero can play the files, but if you wish to use Movie Maker, use the XVid codec.