Recording and playback devices are enumerated in Windows environments, and while Windows SHOULD select the proper device depending on the presence/status of devices, this is not always the case.
If none of the below works, you should ensure that your audio/motherboard drivers are up-to-date and functioning properly before trying again.
Try right-clicking on your volume control and selecting
Recording Devices (or alternately bring up your start-menu and typing
manage audio devices or
change sound card settings in the search box to access your sound settings; go to the
This panel should display a list of recording interfaces accessible to your system. Select the device that corresponds to your built-in microphone, and select the
Set Default button near the bottom-right corner of the window.
If you find that this has not alleviated the issue, you may need to adjust your device's properties by selecting it and clicking the
Properties button to ensure that the device is not muted or recording at an excessively low level.
If the device still fails to record properly, you may try selecting the device and clicking
Set up microphone to step through a Windows wizard in order to configure the device.
The pictures and many of the instructions above are from a guide on 7tutorials.com.