tell application "System Events"

   set currentProcesses to name of every application process whose visible = true

end tell

set tmpWindows to 0

repeat with tmpProcess in currentProcesses

   tell application tmpProcess

       activate

       try

           set tmpWindows to count windows

       on error

           set tmpWindows to 1 --> # of windows to try to force closed if it doesn't 'appear' to have any windows

       end try

   end tell

   if tmpWindows > 0 then

       tell application "System Events"

           tell application tmpProcess

               repeat tmpWindows times

                   try

                       keystroke "m" using command down

                   end try

               end repeat

           end tell

       end tell

   end if

   set tmpWindows to 0

end repeat