This morning I realized that I have no sound. Was away all weekend and know that I had to reboot my systems to get to the internet. How do I get my sound back?
What exact iMac are you talking about, as there have been many "copies" since 1999?
Have you taken a look at the audio out port and seen a red light? If so, plug and unplug a 3.5mm adapter (headphones, ...) several times until the light goes out.
And what is shown in System Preferences > Sound > Output?