If you don't no how to download the video from www.youtube.com
, just follow the following steps. It will take just 5 minutes and the you will be able to download all the videos from youtube.
1. Install mozilla firefox's latest version.
2. search 'videodownloader' extension for firefox in Google and install it.(You can see all the extensions installed by clicking "Tools->extensions" in firefox browser)
3. Now you will have a small icon at the extreme bottom right corner of the firefox browser when you click on any video in youtube.
4. click on the icon and you will get a download prompt.
5. right click on the 'download Link' button and click "save link as..".
6. save the file as "Filename.flv".
7. You can play this flv file by vlc player.
8. you can convert this file to other video format by some video processing software...
Reply once you are finished as well as if you have any problem...