Videodownloader would only work sporadically for me and I didn't want to download another program.
I found out that Youtube videos are saved in your temporary Internet files folder.
(Tools | Internet options | settings | view files).
They are named something like "get_video?video_id=P7QD9s7KpPQ."
You must copy the file from the folder & save somewhere else (using the extension .flv). To play the file, drag it onto FLVplayer.
It is a cumbersome process
, but it does work!