go here:
http://www.avsim.com/ search the name: Dave 'Opa' Marshall
look for: altitude_callout.zip
Quote from file ID:
"Hear altitude callouts - from your trusty co-pilot) - at 400, 300, 200, 100, 50, 40, 30, 20 and 10 feet above the runway. This can be easily done to virtually any aircraft. You may already have the necessary FPDA sound and gauge files but if not, they are included. Just unzip to a temporary directory (using folders option) and follow the very simple instructions, Compiled for your flying enjoyment by David "Opa" Marshall"