This worked for me too.

I had the same problem and now all works fine. In order to make it work (the Audio tuning wizard didn't fix it) I simply recorded a video I was viewing on the screen first as an audio file. After that excercise (which caused me to do the audio tuning wizard again), everything got set accordingly and when I then recorded (the same video) the sound was there. For some reason recording as the audio only (wma) caused my settings to stick for the subsequent video recordings. I called a friend who had experienced the same difficulty and it now works for him too.

I believe that this tip will enable a lot of people who try and then give up on this trial, because of no sound, to now buy the product (I am paying for it immediately).