
You can download videos from MySpace or YouTube using Firefox browser.
Firefox has a download plug-in called Video Downloader. Once installed, whenever you visit a page that contains a video, you can click on a VideoDownloader icon at the lower-right corner of the browser. This will result in a pop-up window that contains a link that will start downloading the video.
The videos are in FLV format. So you will need to get an FLV to play them.
Hope this helps.