This records whatever device is active and can save as WAV or MP3 at various bit rates.
Home: https://github.com/marc365/Windows-DesktopRecorder
Softpedia: http://www.softpedia.com/get/Multimedia ... rder.shtml (it's a little out of date on formats)
Status: portable, not stealth
The program is DEAD simple and has no settings to write apart from the location of the last recording spot.
EDIT: I tested this with Skype and it worked great.