Here's my best advice.
Try out EasyMovieConverter.com . It is a free online converter that is on the web page so there is nothing to install and is totally safe. It uses the HD versions of the Youtube videos, so you get a true 128kbps stereo and the highest video quality hands down. There are many options to boot such as mp3, video for windows, iPod, PSP, cell phones, and even MOV for mac.
Just a quick how-to to get up and using it fast:
1. Grab the link/website address to the video to convert from Youtube.
2. Go to http://www.EasyMovieConverter.com and enter the url on the text box on the main page.
3. Choose the type to convert it to.
4. Hit the download button. When it is converted, a button to proceed to the download page appears.
5. Download it, and enjoy.