I just serviced an HP that had the same problem. The HP recovery HD had ato be bypassed by installing a fresh copy of Windows and installing a PCI soundcard. Works fine for now but I am waiting for the phone call that other onboard functions are faiiling as well. If I were you I would nip the problem in the bud and get a new mobo while you are still up and running. That was my recommendation to the client but given that it is an HP and a Micro ATX case, it's gong to involve a new mobo, psu and case. HP..........horrible!!!!
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.