Go to Start, type dxdiag and open the utility. Click the Sound tab and check your sound card model. After that, navigate to the developer web page and download and install the latest drivers available. Restart your computer and go to Control Panel > Hardware and Sound > Sound > Recording tab. Right-click the window and check the Show Disabled Devices option. After that, select the microphone icon and click the Set Default button. Also, make sure that the device is enabled (double-click the microphone and select Enable from Device usage).