I have an Apple computer at home that won't let me run 'AVC'. I tried finding something comparable for Mac but couldn't. At the AICT conference, the facilitators for my break-off session mentioned zamzar.com and youconvertit.com. They both can convert files from the web or from your computer. They will send a link to your email for where you can download the desired converted clip. I used both for my multimedia project. Why both, you ask?
Zamzar was a lot easier and more efficient for getting files off of Youtube. It gave me problems when I tried to convert the 'flv' file from Youtube to a 'wmv' for Moviemaker. Moviemaker didn't not want to recognize this wmv. Perhaps zamzar converts it to an old form of wmv or a new updated one that the board computers aren't able to read yet.
This is why I also used youconvertit.com. I converted the files taken from Youtube with zamzar into video files I could use with Moviemaker. Why the wmv videos worked with youconvertit and not zamzar, I don't know but that's how I did it. If you need to convert and you don't have access to the 'AVC' program, try out zamzar and youconvertit.