A bit back I posted a thread asking for help with a problem I've been having with my HD Pro. Basically, I was getting a high pitched buzzing in the background of the video, it was about a quarter to half the volume of the actual game audio. I tried some of the suggestions of the help thread, but no avail. So, after a bit of a break from recording, I tired something out, and it worked!
In the capture software (cant upload pics right now, so I'll Gyazo):
Turn the capture Audio all the way up, and capture.
Convert to MPF to make it work in Sony Vegas.
Finally, in Sony Vegas (or as demonstrated here, in Windows Media Player)
Set the Audio to about 10%, this will cancel out the buzzing but you will still be able to hear the gameplay audio!
Thanks for reading, and if an Admin could sticky this, that'd be great!