One free and simple method to download YouTube videos to your HD (there are others):

1. Use Firefox mozilla.com/

2. Get and install this Firefox Extension: VideoDownloader addons.mozilla.org/firefox/2390/

3. Watch your video on YouTube and click on the VideoDownloader Extension at the bottom of your Firefox bar

4. Save your video and rename it with the file extension ".flv" according to the instructions

5. Use the media player which plays anything to watch: VLC videolan.org/

Optionally convert your video with a conversion tool into another format

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