This is probably the most frustrating computer problem I've ever had with a computer. For months now any microphone I use on my Alienware 13 is not being recognized in my device manager. Whenever I'm in Skype calls with people, they can only hear me through my computer mic even when I'm using a headset with a mic. I've tried showing disabled devices, downloading drivers, using different mics, and basically anything else I could find over months of searching.
Have you tried changing the Recording Devices settings instead of going into Device Manager?
- Connect your headphone with mic in your laptop, right click on the speaker icon on the bottom right hand corner and select Recording Devices.
- Once opened and if you see your mic for your headphone, right click on it and select Set Default.
- Click Apply and OK then test it again.
If these doesn't work try to uninstall/reinstall the sound card driver of your laptop.
- Open Device Manager and uninstall the sound driver.
- Download and install the latest driver for sound from Dell's Support site.
- Once installed reboot your laptop for all the changes to take effect.
- After the reboot make sure that the mic for your headphone is set as the default recording device.