The youtube video can be downloaded using the tool provided by:
http://keepvid.com/
1. firstly get the internet link for your youtube video. For example:
Apologize - One Republic
2. copy and paste the the link into the textbox on keepvid.com website, then select youtube and click on "Download".
3. click on the "download link and when it finish, rename the file get_video as "Apologize - One Republic.flv".
You can now play this video using K-lite codec pack player or convert it to other format using any video converter software (See previous article). The K-lite codec pack is available on:
K-Lite Codec Pack