How do I extract audio from a you tube video-have flv extract but won't play files sent by flv player?

Have downloaded flv extract, it won't recognise flv files saved from flv player-keeps coming up this is not flv file-need help to convert video to audio from you tubeJust Use E.M. Youtube video download tool. It works great and easy to use.It can download video from youtube , myspace, veoh, yahoo or any other video websites autoamtically.And can also download, convert, burn,search, repair and play any youtube video.Convert flv, mp4, mov video to any audio include MP3, wma,wav,ac3,mmf,amr,ogg,aac..., to any video formats include 3gp,avi,wmv, mpg,mpg4,asf,swf,h264,mov,jpg, that can be flv to mp3 support by PSP,iPod,iPhone,Apple TV video,iTune,MP3,MP4,Zune,Cellphone,Digit... camera,DV,CD/DVD/VCD/SVCD..