I recently had problems in recording audio with Windows 10. In my case the recording software was PowerPoint, whereby the screen recorder generated videos with no audio.
After some wasted time, I figured out how to proceed. First, to set “what you can hear” as audio source (and therefore NOT the microphone) you need Stereo mix as audio input, but it was nowhere in my windows 10!
To solve this problem, go to Device Manager and update your Audio driver. Now Stereo mix should be available, so go to Sound (type it in your windows search bar) then to Recording (Aufnahme in german) and activate Stereomix (I also disactivated the Microphone).