Two freewares, who do the job for you. YTbuddy is the more primitive version, but you encounter less problems than with TubeEmAllPro (the more sophisticated and 'better' of the two). But you can run the two of them simultaneously. Try them out and be surprised.
By the way: The manual is pretty lousy, sorry. For manual and download go here [www.tubemall.net]
Depending on your download speed and the ressources of your PC you can get thousands of videos in a couple of days. But you will have to rename them, that's the problem. Otherwise you will later hardly ever find again, what your looking for.