thanx water_dragon
at least someone feel this one are useful :P
anyway this snippet will downloading a .flv file(which that was a youtube video file format) and that means you need a FLV player which like mountaindew suggesting you can try total video player or you can google for \'flv player\' or you can get a codec that supported the .flv player such as storm codec.

water_dragon you can renamed the file as any .xxx that you like, however you still need a FLV player to play it. Even if you rename it as .wmv(for example) and your player didnt support flv format then an error occured.

If you want to convert the downloaded file, once again u can follow what mountaindew said. Or you can try media converter(which im prefer :P), you can get it at http://www.mediaconverter.org/ (either you want used the online converter or download its free version)

For others, there was some major problem for the url this snippet echoing(at @getvid). Since any url that have a spaces are not being converted into url form so a clicking at it will not working(eventhough its work but its redirect the browser to a wrong url).... So its better used the \'-b\' switches for this moment(until Ive got a desire to recode this thing-got many video to download so cant have spare time to coding lol :P)