I bought a Mac Pro (2007) and I understand that it does not come with a mic in port. It comes with a stereo analog line in port. I see this also when I go into System Preferences --> Sound I've tried plugging in my acoustic electric guitar to the line in directly, but get nothing. I tried this because everyone has told me I could, including Apple. People are doing it with their iMacs and Mac Books, but it doesnt work on my Mac Pro. Are the ports on a Mac Book a combined mic in and line in port? Thats what I am lead to believe. What is even more interesting is that I went to the Apple store yesterday and look at a 2009 Mac Pro. I went to System Preferences --> Sound --> Input and actually saw an entry for "Built In Mic". Can anyone with a 2009 Mac Pro confirm that? Does that mean the new Mac Pros have dual functionality in these ports (like a Mac Book)? Can anyone confirm this?