I'm going to just write that the Realtek audio input may not be working. Causes could be blown input to setup issues. Be sure you check the mixer. Remember that the controls are not standard so I can't write any specific.
I'm running windows 10 Pro on a HP w/ 2 hard drives and 16MB ram.
Here's my issue--- I've got a Samsumg 32" monitor as one or my two monitors for my pc setup. I thought it would be cool to attach my cable DVR receiver to it to watch and record tv. HDMI connection from box to monitor works fine. But I forgot the sound component. No sound. The cable box has the traditional optical out and RCA/Composite Outs. I got an RCA to 3.5 adapter to plug the sound into my sound card (Realtek) audio in jack, but nothing. As a test, I plugged the RCA to 3.5mm adapter directly into my cheap computer 3.5mm in port and got sound. Poor, it was, but I did get sound. The connection and location aren't feasible to make this a permanent solution. So, why isn't it working through the tradition audio in port on the computer?