A while ego, I added 2 videos showing an easy way to convert a video into yor PC. You may store the video as movies or music such as mp3.
This is Downloadhelper , the one click downloader. Let me tell you the big deal about this extension, if you can play a file ( by file i mean movies, videos, mp3, and so on...) on your web browser, it can save it. It is not just for you tube.
Downloadhelper is Add-on for Firefox (Firefox is a Browser for those who don't know). There are other extensions and 3rd party websites that claim to do the same thing, but this one is the Best, its fast and very simple to use.
Be smart, you can use this extension with a lot of websites out there, not just with youtube, myspace, dailymotion, etc... You Find something on the web you like, Downloadhelper will do the trick.