How are you recording your audio? USB Webcam/device, bluetooth, or analog jack? Have you tried using a different input device or PC?
What kind of soundcard does your PC have?
Have you disconnected all audio in/out devices, save a mic/headphones and attempted to record from that configuration?
I know that you have gone through an external system (from PC) and are getting the issue, I am thinking the most direct may help.
I have a few different options. I have an external E-MU 0404USB, a webcam and the on-board SoundMax audio. The Presenter options are horrible, only giving the choice between two: line in and mic, and it doesn't mention what device it is or the level. Shocking really. So, as far as I can tell, the line in is always going to be the line in on the SoundMax audio. The mic however, I could change between the external E-MU, the webcam and the on-board mic input. Niether the line-in setting or the mic setting in Presenter will record anything though. It's just loud noise no matter what device it's set to, or what device is configured as the default mic in Windows.
I had the same problem but now I use a Behringer Ultravoice XM8500 routed through a Mobile Pre USB audio interface by M-Audio on my Dell laptop and get clear, static-free sound everytime.