The short answer is that youtube videos aren't meant to be downloaded, and are usually the intellectual property of the poster. I would suggest sending a message via youtube to the video poster and requesting a copy of the video file. Explain to the poster what you intend to do with the video and why. If they are willing to send you a copy of the video file, then from there you would want to use DVD creator software if you want to make it a playable DVD. You may be able to find a free DVD creation program from Cnet's download.com