This program converts automatically Youtube videos after downloaded.
http://29984.rapidforum.com/topic=102373698317

But if you search a flv to avi converter, there is a program here:
http://www.gezginler.net/modules/mydownloads/singlefile.php?download=freez-flv-to-avi-mpeg-wmv-converter&lid=4293

KaDear