do you have a sound card installed? if so which one. is it the integrated one? you can go to your device manager and see if its enabled. however, I would actually recomened you email HP customer support with your problem. I have dealt with HP customer support a lot in the past, its free (email, phone is charge unless you have warranty) they are very helpful, sometimes slow in reply, but very helpful. every time ive emailed them with a problem they helped me get it fixed.
Sound Help, Im desperate. 
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