Acer aspire 5720z audio video problem

Question

when playing audio or video (includes dvds) every couple of minutes the audio will distort and after about 20 seconds return to normal in the case of video it slows down to few frames per second and then in approx same as the audio will resume normal speed. this problem also seems to affect the XP system sounds as well. I switched from VISTA to XP and used the drivers on the US web site.