Hello I recently purchased a GT70 2PC running Windows 8.1 and was experiencing similar issues regarding low mic input volume. I scoured the internet for possible solutions including uninstalling drivers then reinstalling them, the works. The good news is I may have found a possible solution. All of the threads I have read spoke of people modifying the mic input volume through the Realtek software but the issue may actually be on the Windows side of things. Check your mic gain under Control Panel => Sound => Recording => Select Microphone and configure. Under "Levels" tab, check and see what level your mic gain is set to. If it is low, adjust accordingly and apply changes. I noticed Windows, or some other application, would lower this gain, not Realtek's, thus creating my low mic problem. After adjusting the aforementioned gain, my mic works wonderfully =P. I hope this helps!!