Can't reset PRAM with Microsoft keyboard, lost sound

I'm having issues with my internal CD burner, keeps popping disks out after about 30 seconds every time I put one in. I decided to try and Zap the PRAM. I have a Microsoft 3000 keyboard (which has worked well for some time now), I checked it's preferences to make sure the Windows key = Option and the Alt key = Command. I tried to reset the PRAM ( Opt, Command, P,R, at start up) but I didn't get a second "gong". When I logged in I found I no longer have sound or volume control. I've tried several times to reset the PRAM, but still no second gong and no sound. What's up? How do I get sound back?