If there is a build-in microphone, go to Start > Control Panel > Hardware and Sound > Sound and select the Recording tab. Right-click anywhere in the provided window and select Show Disabled Device. If you are not able to see the microphone, reinstall the camera driver and reboot the PC. After that, double-click the device from the Recording tab and select Enable from Device usage. Also, click again the microphone icon and press the Set Default button next to the Properties option.