Screencast - recording microphone and audio output at the same time

This demonstrates how you can record what you say into your microphone as well as the sounds from your pc - for example winamp.
This is relevant to podcasting as well as screencasting.
http://www.myscreencast.com/forums/viewtopic.php?p=51#51
http://www.myscreencast.com/nev/audacitytest.wmv