How to fix if the computer loses sound.
For Vista, Windows 7/8/10:
Click the small trumpets under the right corner on the desktop, select Playback device and change the playback device to the default one.
For Windows XP:
Click the Start menu, select Control Panel > Sound and Audio Devices > Audio Option and set Default device as the physical card of the computer.
If the above doesn't help, please click "I need direct assistance" button and attach the screenshot of the sound device list under Audio Option or Playback device tab for further assistance.