The avi is most likely busted up. It didnt record properly most likely.
If I may offer a bit of advise... Dont use the film viewer to get your avi's. Use a stand alone recording program such as fraps that records what you see on the film viewer while its playing.
Go to
http://www.fraps.com. They have a trial version and its free. You can record short clips up to 30 seconds long. If you want to record anything longer than that you must purchase fraps for I think around 30 bucks. Chump change for such a handy little program.
I'm not skuzzy, he might tell you something different.
But if you want quality, ease of use, and an idiot proof way of making films, thats the best way to start your projects.
Fraps isn't editing software. It only records in avi format. Once you get your Avi's together you can then import them into any one of the film editors you have... Windows movie maker or what have you.
GL.