Despite your checking the Troubleshooter, I'll suggest a couple of obvious
things:
- Check your volume icon in the tray to be sure you haven't muted the sound
- If you have external speakers, check the connections to be sure they are
fully connected, and not shorted out.
- In Control Panel, look at all the options in Sounds and Audio Devices to
be sure the settings are what you wanted.
- Check the operation of your audio devices: Click My Computer/View System
Information/System Properties/Device Manager/Sound, Video and Game
Controllers. Double click the items listed for a report on their operation.
If you see any warnings, a "!" in a yellow triangle, you have a problem. See
if it tells you enough to solve the problem.
- Have you installed new software recently? Try restoring to a date well
before you last heard from your system.
Good luck.