Here is a program that uses the Windows API function EnumWindows to find and return all top-level windows  or running programs.    Calls to EnumWindows take two parameters, a pointer to a callback procedure which is passed the handle of each top-level window and an arbitrary parameter which I use to pass the address of a Tstringlist to hold the results.    

I made three versions of the callback procedure called from three different buttons - NextWindow builds a list window titles, NextProgram builds a list running programs, and NextBoth builds a list with both.       Callback procedures must be specified with stdcall  so that parameters passed by EnumWindows are interpreted correctly.   

The code to retrieve the program associated with a window handle is contained in function GetWindowExeName which returns a string representing the executable name.   The details of this function are a mystery to me - I lifted it from the Delphi section of experts-exchange.com  with a minor correction or two.   I filter out duplicate occurrences so that only each program only appears once in the resulting list.    

A final button tests the main motivation for  this program; an  IsRunning function which takes a program name as a parameter and returns true or false depending on whether that program is currently running. 

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