No sound ... at all?

Hi folks,

I'm new to macs, this being my first one (well second if you count the one I just returned for a fan that would go full blast non-stop) and now on my new mac I get no sound whatsoever. I click on audio(built-in) in the system profiler and it says I have no built-in audio. I get no start up chime, I can't play any iTunes, nothing. When I connect my HT receiver it doesn't register that there is a digital audio device connected, though it worked fine on the one I just returned. I even tried connecting my Ipod headphones and they were not identified either.

Is there something really simple that I'm just missing? I confess to not being the most computer literate guy around, so I'm hoping someone can help me, I really don't want to return another mini.