function EnumWindowsProc(Wnd : HWnd;Form : TForm1) : Boolean; Export; {$ifdef Win32} StdCall; {$endif} 
var 
 Buffer : Array[0..99] of char; 
begin 
 Result:=False; 
 GetWindowText(Wnd,Buffer,100); 
 if StrLen(Buffer) <> 0 then 
 begin 
  Form.ListBox1.Items.Add(StrPas(Buffer)); 
  Result := True; 
 end; 
end; 
 
procedure TForm1.Button1Click(Sender: TObject); 
begin 
 EnumWindows(@EnumWindowsProc,LongInt(Self)); 
end;