I have been able to get video from video.google.com but not youtube.com as yet. The Google videos are already on your PC in \Documents and Settings\YOUR_USER_NAME\Local Settings\Temporary Internet Files\
They are in .FLV format ( Flash Video ) but aren't named so you'd recognize them. Sort the folder by file type and then you can find all the .FLV files you have been watching. If you have been watching a lot then maybe you should delete all the FLV files and then just rewatch the ones you want to save so you know you are only converting the ones you want.
Riva encoder is free software that will convert .FLV into .MPG
http://www.rivavx.com/index.php?encoder&L=3 Copy the .FLV file into some other folder then browse to it with the Riva Encoder. Then change the output name to something.mpg and click on Encode. And be patient because it will take quite a few minutes. At first I thought it had frozen but that wasn't the case, it just gives no indication it is doing something. I'm just not sure yet how to get Youtube.com files.
[This message has been edited by Nigel (edited 07-30-2006).]