Just a wild try, but it takes almost less time to do than type the instructions: Change the default recording device in your Control Panel Audio to any other you might have on the list. Save, maybe even reboot with the new setting. Reopen the Control Panel and change it back to what it was. Save.
You said earlier you can hear your voice depending on your settings. I guess that means "Microphone" unmuted in the Playback mixer. So the microphone should work... Strange.
You could also try the following: Go to Device Manager, ->Sound, video etc.->Hilight Realtek High Definition Audio and remove it. Reboot and let Windows reinstall the existing driver. If the installation fails, your installed driver has some problems which you should be able to correct with the motherboard driver disk.