Dell Latitude D520 notebook - Windows XP Home - only about 6 months old. All of a sudden, sound doesn't work. Well, system sounds come through but there is no volume control in the task bar. Control Panel - Sounds : everything is greyed out and it says "No audio device". Device manager does not show any errors; under Sounds, it lists several items and says they are all working properly. Tried the Windows troubleshooter for sound, but when I click on the link for Volume Control, it says "there are no active mixer devices available". Read all the posts here on that subject with no help. Downloaded the SigmaTel driver from Dell (the only sound driver listed when I searched based on service tag). Installed the driver with no errors. Rebooted. Still no sound. System is free of viruses, adware, spyware, etc. This problem just cropped up and I have no idea why.