I have been messing around with this problem the whole day now and still nothing.
My problem is that i have a Chaintech 9PJL1 motherboard with the C-Media CMI8738 audio chip (checked it with Everest). I just changed my OS from Windows XP SP3 to Windows 7. I can't get any sound out of it anymore. It worked perfectly fine with the Windows XP.
I tried to download the latest audio drivers for the CMI8738 audio chip from this site: C-Media Company Information
I even tryed to download the XP drivers and run it in XP compatible mode (both SP2 and SP3) but it gives me the same error over and
over again "Please plug-in the c-media audio device device".
I also tryed to update the drivers under device manager and with windows update.