There are lots of tools out there for downloading YouTube videos to your computer. Many of them cost money, others purport to be free, but require you to install software on your computer — something you should avoid doing unless you are absolutely certain the program is safe.
One apparently safe no-install utility that I've used, which you may find useful as well, is SaveFrom.net. You simply paste the YouTube URL into a textbox, and click the "Download" button. Information about the video will appear below the button, along with links to a selection of available formats. Click on the desired format, and the video will start downloading to your PC.
It can't get any easier than that.
It can't get any easier than that.