I use
Video Downloader to save the files from YouTube. Very simple to use, copy the web address into the Download box, click download button and download. This saves the file as a .flv which is viewed using something a flv viewer eg GOMplayer.
Alternatively you have the option to convert to an avi which can be watched on using Windows. Must admit I haven't tried that as I watch them on GOMPlayer
All the links to the YouTube are in post #123