i had a lot of probs with Realtek hig def audio drivers and windows vista 64, in the end my only cure was to disable the hardware in the bios and install a third party sound card.

sucks but it worked a treat. not a great help for you on your laptop though i know...worth checking you have new drivers available? HP will have drivers for your laptop at their website, just checked and they have drivers for dv6700t, if thats yours?
Kind Regards
Paul