Plug in your headphones and follow these instructions: ......."Without touching anything, run WINDOWS UPDATE and let it download all files that it presents you. Shouldn't take too long with broadband. After the updating, there was a new item in the 'audio devices' hardware, in control panel, called "C-Media USB Sound Device". Since then, the AC-850 has worked like a dream. Now, when I plug it in, a new volume panel opens when I double-click the volume icon."

This excerpt came from this review: http://www.epinions.com/content_232086474372

This is the only fix I could find and if you have already performed the steps, then I'm afraid you may be out of luck.....