When the sound is muted, the sound icon has a mute sign over it. If the sound icon is missing from the ‘system tray’, and it gets back on resetting the laptop, it indicates a driver issue.
• Click Start, click ‘Run’, type ‘devmgmt.msc’ and click OK. (For Windows Vista and Windows 7, type ‘device manager’ in the start search field)
• In the Device Manager, expand the ‘Sound, video and game controller’ section or any device listed under ‘Other devices’ with a ‘?’ or a ‘!’.
• Right click the driver listed under it and select ‘Update driver software’.
• Follow the ‘update driver wizard’.
• If you get a message that the best driver software is already installed, right click the driver and select ‘Uninstall’ instead of ‘Update driver software’ and restart the computer.
• If the problem still persists, download the sound driver from the computer manufacturer’s website, install it and restart the computer.
Hope it helped.
Here’s to Good Karma - iYogi Active Response Team