FOLLOWING ARCHIVED ON BCUG GENERAL BULLETIN BOARD WWW.KEEPVID.COM

(Steve, 5/20/2014) MOST YouTube videos are easily captured using www.keepvid.com 

“copy” the URL for the YouTube video  (sometimes the URL for embedded videos are hidden- I sometimes retrieve the URL by right clicking the video image)
Browse with Google Chrome (with all java plug-ins enabled). 
Browse to  http://www.keepvid.com
enter the YouTube video URL in the TOPMOST small box – then click the download box on the top right (everything else on the screen is adware)
ALLOW or RUN all of the resulting Javascript prompts
Choose the resolution you want to download.
NOTE: I also use these same steps to capture ONLY the music associated with a video.  I choose the “resolution” with the label “MP3”
(AGAIN- be careful to NOT install any of the resulting adware – unless you want additional software on your PC!)

Bill Silverman's comment: In the past, using windows XP, I often was able to capture YouTube videos in very good resolution using "KeepVid", a program recommended by someone (probably Alex or Joshua) at Photodex a few years ago. I have made many educational slide shows incorporating really great clips this way, but since using Windows 8 and 8.1 I haven't been pleased with the results of the captures.

Firefox plug-in called Video Download Helper (VDH).

Once the plug-in is installed, a VDH icon is pinned to the Firefox tool bar. Whenever a video is played within the browser, the VDH recognizes it automatically and the icon color changes. If you want to download the video, click on the arrow next to the icon which displays the name of the video. Click on the name and the video will be downloaded to your computer. The file will typically be in flv (flash video movie) format. Firefox has an add-on that downloads youtube clips with one click. https://addons.mozilla.org/en-US/firefox/addon/download-youtube/
The feature puts the download button on each clip. Just click, choose mp4 or other and the video downloads

FIREFOX AVAILABLE FORMATS AND RESOLUTIONS:
* MP4 360p (480x270, 480x360) - all videos are available in this format. Use it if you want to play videos on an old mobile phone (iPhone 3GS, HTC Desire, Samsung Galaxy S2) or to save space.
* MP4 720p (1280x720) - HD format, available for an increasing number of videos. Use this format if you want to play higher quality videos on a tablet, laptop or a phone with HD display (Samsung Galaxy S3, Galaxy Nexus) or almost HD display (iPhone 4/4S/5).
* just in case you need it, you can also download the highest-quality FLV version available: FLV 240p (426x240).
* 480p and 1080p are no longer available as standalone videos downloaded from youtube.com. YouTube switched to adaptive streams and uses separate files for video and audio, which need to be merged to get a video file. This is more complicated and requires more advanced tools (ffmpeg), so I haven't added them yet.
 

Any Video Converter (AVC)

 VIDEO FORMAT CONVERSION: To play downloaded video clips using the MS Media Player,  clips need to be in WMV or MP4 format. To make format conversion, I installed Any Video Converter (AVC)

For a 5-min YouTube video clip, FLV to WMV conversion takes 30 sec or so.

SCREEN CAPTURE: "LiteCam HD" captures ANYTHING on the screen. Adjust frame to enclose the part of the screen you want to capture. Click record. Resolution is better if you don’t try to capture full screen.

GENERAL COMMENTS: Alex at Photodex: Streaming video sites like YouTube continually improve their security measures to prevent the use of video download programs, so it's always going to be a bit of a cat-and-mouse game. On top of that, some accounts on YouTube - especially major television networks and music labels - seem to employ an even higher level of security