My laptop's combo headphone/mic jack isn't allowing my headset's microphone to detect sounds. I've tried reinstalling the audio drivers and messing around with the settings. The headset is a Logitech g230 with a separate audio and mic lines, and I have an adapter to plug that into the combo jack. The sound works just fine, the mic never works. My laptop is an Asus GL551 and the audio driver is the latest version by Realtek.
My solution for Windows 8.1 was(for Asus N551JK but actually should work with any Asus notebooks combo jack sockets, not sure regarding other manufacturers because driver installation step is important as I was not able to get to work microphone from my 4 pin headset before driver installation):
1.Download driver for your OS from manufacturer official page
2. Install driver with all reboots that it may require
3. Connect 4 pin headset and check that mic is working now(for me no new microphone was installed in system(however in Realtek dialog I have chosen "Headset" option), but green scale at the "Sound" dialog on "Recording" tab start actually working for connected headset's microphone.
4. In case you use audio splitter cable MAKE SURE that it is 4 pins jack to 2 sockets x 3 pins(read it's descriptions or at least see that sockets is signed by mic and headphones/speakers icons or one is red and another is green like this one:
DON'T USE splitters with not specified mic and speaker outputs because most likely they just split signal(i.e. have the same output sockets pins amount as amount on it's input plug. For example: 4 pins input to 2 x 4 pins output)
I verified both the cable and my mic works by plugging it into my phone. Two days ago it was even working with my laptop, however the next day it stopped working again even though I didn't change my audio settings after it started to work.