It's very easy to download youtube(or any other flash website) video, and just click to play video.

1. Run iNetGet;
2. Play video on any browser like IE, FireFox, Opera, ...;

then the video will be sniffed and downloaded when it starts to play.
Example: if you have installed and run iNetGet . Just visit http://www.youtube.com and play any video.

(Tips: If the video isn't sniffed, try refreshing the webpage and make sure the video is playing.)