On my Acer laptop it also has the Realtek app for speaker setup etc. In the windows Sound app under the Recording tab, it shows Microphone as default device. Line in is grayed out and shows "Not plugged in".
Cameronfol, do you have anything at all plugged into any of the audio jacks on that laptop? On a laptop a lot of the time if you plug in external speakers or headphones the built in speakers get disabled automatically. Same thing with the built in Mic, if you plug something into the Mic jack it turns off the built in Mic. Its an either or thing. So if you plugged something into the wrong jack (the Mic jack) you could end up with no working Mic. Can you tell I'm running out of ideas.