I had the same issue with my Dell. What was happening was the default sound device was not switching to the proper device/port when headphones where plugged in. Part of the issue was I was using a D-port to my monitors that had integrated audio (similar to some HDMI) and the sound was playing on the monitor jack instead of my headphone jack on the computer. So I ended up right clicking on the speaker down near the clock --> playback devices --> Click on the port you want to be the default --> click set as default. I know what your thinking, they both say Speakers which one is it? Play some music and you will see the green bar jumping on the output that should be making sound. If you don't hear sound, set the other device as the default. For instance, in my example. The top speaker are my monitor speakers, the bottom, the built in laptop speakers.