Well if that just happened out of the blue their is a problem and I doubt software will fix it just cover it up there is probably a loose connection somewhere unplug your headphones and plug them back in then play with the connector a bit while you have the headphones on and see if the sound returns. You can use windows to change output to a certain speaker. To do this just right click on the speaker icon in your taskbar, choose playback devices, right click on your headphones (it will probably say speakers/headphones) click on properties, go to level tab, select balance and change it.