I get this, too, every 30 seconds, using Windows Media player to play tracks stored on hard disc, or when playing videos on youtube. Dell 1545 laptop running Windows 7. Windows task manager / performance graph shows a spike in CPU usage, corresponding to the hiccup in the sound, like the needle going over a crack in a 78 (showing my age here) or a scratch on a 45rpm single. Very irritating. Please someone - tell us a cure.