No sound vista Realtek

I have a new HP and my sound quit after 3 months. I've tried all the online support help with HP and reloaded drives for my Realtek. I just sent my computer back to the factory and it was returned with the same issue. My mixer board indicates their is a signal and all the components show its working fine. I've tried 3 different headsets so I'm not sure what the issue is. Could this be a motherboard issue? Please help me what I should try next.
Thanks

If you go to the control panel, click hardware and sound, and click manage audio devices what all shows up? You should have at least 2 items; speakers and "realtek digital output(RCA)". From your description it sounds like you are seeing one or both of these and they indicate they are "ready" but you get no sound if you plug into them or right click and select "test".

If using the realtek hd audio manager I'm guessing you see the audio outputs as active. If you haven't already try changing your default output format to a 44100hz signal. Have you tried the digital RCA output?

I get both options. I use a headset vs speakers. I've tried all 3 headsets and none work. when I test the speakers the computer indicates all is fine. my driver is a 6.0.1.5657. I really not sure what to do anymore. I've tried a USB headset and luck either. HP has done nothing for me. I ready to send my computer to the CEO of HP with a letter telling him he can have this piece of junk.