Not trying to step on Sting's toes here, but if you use Firefox, like I do, there's a plugin called DownLoadHelper that is very easily used to download YouTube videos to your PC. This is their homepage:
DownloadHelper - Media download Firefox extension. It's free, though they'd like a "donation", no ads, and doesn't seem to install any spyware or other malware.
And, to view ".flv" files and other formats too, I highly recommend VLC Media Player from here:
VideoLAN - VLC: Official site - Free multimedia solutions for all OS!. It's open source, no ads, no spyware. They'd appreciate a $10.00 donation. It plays virtually ANY video file, including ".MOV" and ".mp4". I like VLC much better than FLV Player.
- Jack