Youtube video download without any plugins 100% working

Tired of installing plugin's and viewing the youtube vidoe, when its nice again need to download...
Save your bandwidth data too.....

1. Wait for the flash video loading completely, i.e. able to play MTV to the end
    
2. Open a new tab / window of Firefox and enter about:cache as an URL
    
3. Take note of the Firefox cache folder path specified in Cache Directory: and browse to this folder with Windows Explorer
   

   
   If the Storage In Use greater than or approaching Maximum Storage Size, the video might not be cached completely or you’ll have to increase Maximum Storage Size and reload the MTV again.
   
   To set Firefox cache folder maximum storage size, click Tools | Option… | Network | Cache

4. Sort the cached files by file size and try to open the biggest file with Storm Codec-MPC or FlV Player. (The biggest file is likely to be the cached YouTube video)