ASUS UX303L, sold with win8; after win 10 update notice microphone missing from recording devices and device manager. Only Speakers (Conexant Smart Audio HD) under audio inputs and outputs. Under sound video and game controllers there was Conexant Smart Audio HD and some Nvidia virtual audio device. I downloaded and installed the newest win8 drivers from ASUS (win 10 STILL not available), this got me a "microphone" that was "not plugged in", like a jack mike on a desktop PC. I tried windows update, that did find newer drivers, but alas no change. Finally I uninstalled everything from Audio Inputs and Outputs and Sound, Video, and Game Controllers in Device Manager, checking the box to delete the drivers, and scanned for changes. This got me WORKING mic and speakers under the generic, in-box windows drivers, then it found new Conexant Smart AudioHD drivers (8/4/2015 188.8.131.52) under Sound, video, and game controllers and while i allowed the install with some hesitation, it did get finally get me functioning "Microphone Array (Conexant SmartAudio HD)" and "Speakers (Conexant SmartAudio HD)" under Audio inputs and outputs.
Hope this helps someone. Just wish ASUS would do the due diligence to post up a working version for win10.