I haven't used MC6 for a while and am lost to many things. I was just looking back through some old files and somewhere in the mix I changed some parameters with the audio. To start with, I have audio everywhere but MC6. When I click on a file, it starts up MC6 and I get the following message: "There are no audio devices for the current  driver model on you system. Please go to options/audio and chose a different model." Options/audio where in MC6, or in the computer. The only tab I have for options in MC6 is in "track view". I see no other places to change anything.

start in the computer
 

Somewhere around MC 6 or 7 they changed the options selection from a tab at the top to a keyboard shortcut. If there is no 'Options' tab at the very top, try pressing 'P' on the computer keyboard.
Do you know what sound card or audio interface you're using? If it's the computer's sound card and the audio driver is ASIO, or even WDM/KS, that may not work with many stock sound cards. Then you're stuck with using the MME driver mode, which is a terrible choice for live recording due to it's inherent latency.
And welcome to the forum.

You didn't mention the soundcard or the driver for sound that you are using.

Just because you have sound in other places doesn't mean you have sound automatically in MC. You need to have the sound chip or interface set up with the correct driver for it to get sound in MC. 

It took me the better part of 2 weeks when I was getting started to actually get things working correctly.  You have to set things up properly in the computer as well as in the MC software and in the interface's software control panel as well.... that's what was hanging me up..... Once you get it working, you save the settings and it's a non-issue from then on.