I do use Grabthat video. I tried it myself and it really works. Simple and fast.
All you have to do is log on to YouTube. Select the video you want to download. Copy the url on the Address bar. Go to Grabthatvideo.com and paste the YouTube url to the box. Press the download button to start downloading your video. Save the video to your desktop and you can change the filename. In order for you to transfer video files into your computer, you need to download flash player software at Grabthatvideo.com, and take note it is for FREE.
It is simple and fast. Besides, those softwares are FREE.