Sound not working please help!

"I have tried everything" puts it in the "time for the shop" category.
System Preferences > Sound should have been #1 on the list


MacPro 2008 3.1 | 14GB Ram | Quadro 4000 | MC6.0 | OS 10.6.8 | MOTU HDX-SDI | ATTO R644| LaCie 324

 

Make sure you zap the PRAM three times in a row (three chimes). And it might sometimes take even more to get the sound to come back.

 

You wouldn't happened to have spilled water now, would you? Happened to my last laptop. Spilled just a few accidental droplets, I'm talking less than a small sip-worth of water on my laptop while it was closed. Functioned fine but my speakers were RIP since that day.

 

It's possible that...

.... the prongs of the 1/8" headphone jack are stuck & disengaged, thus no sound from the computer's speakers. Sometimes a bit of light "wiggle" of the phone's plug will do the trick. I have even once used a safety pin with it's tip bent slightly to fix the problem you described.

If it's under warranty, let the pro's look at it. My suggestion is a last ditch option as opposed to a possible expensive repair.