|Did the sound suddenly stop and if so, what happened to cause it?|
Did you get the drivers from Toshiba?:
Are there any errors showing in "Device Manager > Sound, video and game controllers"? You could Uninstall the sound drivers in Device Manager, which only removes the settings. You then restart the computer and it sets up the drivers again (finds new hardware). If it asks you to remove SOFTWARE do not let it, otherwise disregard any other warnings.
Always pop back and let us know the outcome - thanks