I cant seem to upload vids straight from my digital to youtube or photobucket. They seem to end up with zero seconds

eg:

http://www.youtube.com/watch?v=TDc_7b9K9T4

They come off the camera in .avi format

If i convert the vids to Mp4 and upload them it works fine eg:

http://www.youtube.com/watch?v=rgcPJDUekqI

anyone know why this is ? Its annoying having to convert them, and the free converter i have puts txt in the middle of the screen. So can someone tell me where im going wrong or at least point in the direction of a free converter that doesnt put a "watermark" on the vid.

Thanks