How do I download high-quality MP4 versions of YouTube videos?
Sign into your YouTube account. Click on your user name located in the upper-right corner of the YouTube window and then click on the “Account” option. Under the “My Account” heading, click on “Videos.” Find the video you want to download in high-quality MP4 format and click the button labeled “Download MP4.” You can download only your own MP4 videos that you uploaded to YouTube. As of May 2010, you cannot currently download other users’ videos in the MP4 format.