There are plenty of software to download video files from YouTube of which I've tried is YouTube Downloader. You can download it for free at http://youtubedownload.altervista.org
Once you downloaded YouTube Downloader and install this software on your computer, run the YouTube Downloader applications.
- In the text box "Enter the URL of the video You Want to download (e.g. http://youtube.com/watch?v=f5Jz8 ...)" fill in the URL link where the video will be downloaded.
- By default the downloaded file will be saved in My Document. If you want to change click the Change button and browse to the new location that you want.
- Click the Download button to start the download process.
Wait until the progress bar is full and there is notice download completed.
With this application you are also able to convert video files from one type of file to another video file type. Suppose you want to convert video file type MP4 to 3gp.