You may have to defeat the motherboard's onboard features from the BIOS, unless that is your intended device. Right click the speaker icon in the system tray and choose "Recording Devices." Make sure the device you intend to use for the microphone is set as default. Go through the configure routine to set up the mic.
Windows 10 update was breaking audio settings with each update, until about August 18. Since then the reports have been fewer. However, if you use the Nvidia 'Express' install routine you will have to use Control Panel to disable the Nvidia playback feature, unless that is your intended device. Express install ignores your current settings and initializes the video card's audio as default.
Also, if you have any Microsoft microphone device (a webcam for instance) Windows 10 will attempt to initialize it at every turn. I think it is a Cortana 'feature' to record your voice, or use face recognition for login. I would suggest that you might find it handy to use a power usb hub to 'self-regulate' Microsoft webcams.