The way that you can capture video that you want to download for Youtube is to go to KeepVid.com and paste the video in the bar at the top. You can then click download to the right of the bar. Don't click on the large green download button, or you will be doing it wrong. The video will load a few seconds then you will have the option to download the video. People can use MP4, Flash, or WebM format.
Youtube Mp3 Converter