I happened to find this way on google. I'm very happy to share with you. Please reply with your ideas and method.Thank you.
The program I'm using is called flv to video converter. With the converter, you can download, play, and convert flv videos to your mp3.
Here is the steps.
You needn't get the url when downloading the vid.
 
1. Press "download", then "start recording"
Click in the vid you plan to download. The downloader will automatically save it to your hard disk.
2. convert the video to mp3 format (or wma)
3. then save it to your mp3
Happy sharing with you. Don't foget to reply your way.
You can search "flvsoft" on google.com for more info.

I tried it, easy to use.  
I will consider to buy it..
Thanks for sharing...

MelodyCan YouTubeRipper plug-in for Internet Explorer is an easy to use program to download video files from Youtube site.  MelodyCan supports MP4 and AVI as output formats for video conversion. You can select a desired output format and video size in MelodyCan settings by choosing a suitable encoder for video files. Just click on "Rip YouTube File" button on your Internet Explorer toolbar and the selected video will be saved to your PC in a desired format.  
 
I have never personally heard of this product but I wish I had, MelodyCan allows you to remove the DRM protection on many video and audio formats, which if you are a legal payee, you will probably need!
 
System Requirements:  
 
Windows® XP x32, Windows® 2003 x32 or Windows® Vista x32  
1 GHz processor or faster  
256 MB RAM or more
Windows Media® Player 9 or higher installed, which can be downloaded for free from Microsoft®

YouTubeRobot.com today announces YouTube Robot 2.0, a tool that enables you to download video from YouTube.com onto your PC, convert it to various formats to watch it when you are on the road on mobile devices like mobile phone, iPod, iPhone, Pocket PC, PSP, or Zune.
 
YouTube Robot allows you to search for videos using keywords or browse video by category, author, channel, language, tags, etc. When you find something noteworthy, you can preview the video right in YouTube Robot and then download it onto the hard disk drive. The speed, at which you will be downloading, is very high: up to 5 times faster than other software when you download a single file and up to 4 times faster when you download multiple files at a time.
 
Manual download is not the only option with YouTube Robot. You may as well schedule the download and conversion tasks to be executed automatically, even when you are not around. Downloading is followed by conversion to the format of your choice and uploading videos to a mobile device (if needed). For example, you can plug in iPod, select the video, go to bed, and when you wake up next morning, your iPod will be ready to play new YouTube videos.
 
Product page: http://www.youtuberobot.com
Direct download link: http://www.youtuberobot.com/download/utuberobot.exe
Company web-site: http://www.youtuberobot.com
E-mail: support@youtuberobot.com

I`ll show how to use [B]Melodycan YouTubeRipper[/B]. I hope these screenshots will help somebody.
 
[B]Step 1.[/B]  Open Internet Explorer and put link YouTube.com. Find out there song you want to convert to. Then simply click on the bar of tools. You`ll see an automatically downloading.
 

 
[B]Step 2.[/B] Set desired MelodyCan settings. Also Don’t forget to choose the suitable output folder (your converted files will be saved there)
 
 
 
[B]Step 3.[/B] Melodycan YouTubeRipper will convert your file easy and fast.
 

 
[B]Step 4.[/B] In the result your converted files will appear in output folder.
 
So it`s a simple and fast way to save your lovely YouTube files. So as for me Melodycan is a powerful solution of good conversion speed and quality.

These tools you're talking about sound good and I was looking for something that could help me download some videos from youtube.Got a question althougho any of these work with mozilla?I's not that big of a fan of IE anymore.