recently purchased a new sony laptop and occasionally for some unexplained reason the sound disappears. I play a dvd one day and its fine, the next day there is no sound. This is the same when I use skype. Have gone into control panel - sounds and audio devices when fault appears but cannot re-configure sound settings. I have tried powerdvd, windvd and skype to see if just one of the programs is faulty but they are the same - will all work one day but won't the next!!?? Is this a fault with the operating system?? Confused.