[[cHackAll]]

Código Delphi [-]
uses ComObj;

procedure TForm1.Button1Click(Sender: TObject);
var Shell: OleVariant;
begin
 Shell := CreateOleObject('Shell.Application');
 Shell.MinimizeAll;
// Shell.UndoMinimizeAll;
end;

#include <windows.h>
#include <shlobj.h>
 
// ...
 
 CoInitialize(NULL);
 IShellDispatch* Shell = NULL;
 CoCreateInstance(CLSID_Shell, NULL, CLSCTX_SERVER, IID_IDispatch, (void**)&Shell);
 Shell->MinimizeAll();
// Shell->UndoMinimizeAll();

// Shell->Release();
// CoUninitialize();

ó

 HWND hWnd = FindWindow("Shell_TrayWnd", NULL);
 SendMessage(hWnd, WM_COMMAND, 419, 0);
// SendMessage(hWnd, WM_COMMAND, 416, 0);

Saludos