Why is the sound not working?
The computer has no sound either on start up or during operation.
I would guess it's one of three things:
1. Double check that the sound isn't muted (unlikely but I had to mention it).
2. A cable has come unplugged in the computer that is preventing audio to get to the speakers.
3. Some component of the sound system needs to be replaced. Whether that be the speakers, sound card, or sound cable would have to be determined by testing.