Yes, if you have an audio recorder such as Audacity installed, set it to record then play the youtube file. It should record the sound for you. Make sure you select the right input first (soundmixer ) rather than ext or mic.
Second way install free version of Realplayer and when ever you have a flash video a small window will pop up to say " Download this file?" press yes at it will save the file to the Realpayer library for you to watch when you are offline. Will allow you to burn to dvd or cd too.
Aunsoft Video Converter helps you convert between various formats. It is the must-have conversion tool for video lovers, and enables you to enjoy movies on computer, to further edit video for creation, to present video on HDTV, and to publish video online in web-friendly format. You can control your video and music on popular portable devices including iPad, Nexus One, HTC Hero, Zune, iPod, PSP, Apple TV, iPhone anytime anywhere.