Как проверить, включен ли ActiveDesktop?

Вариант 1:

Source: https://forum.sources.ru

function IsActiveDeskTopOn: Boolean; 
var 
  h: hWnd; 
begin 
  h := FindWindow('Progman', nil); 
  h := FindWindowEx(h, 0, 
             'SHELLDLL_DefView', nil); 
  h := FindWindowEx(h, 0, 
       'Internet Explorer_Server', nil); 
  Result := h <> 0; 
end; 

Вариант 2:

Source: DelphiWorld 6.0 https://delphiworld.narod.ru/

uses
   ComObj, ShlObj, ActiveX;

// Check if Active Desktop is enabled (2) 
function IsActiveDesktopEnable: Boolean;
const
  CLSID_ActiveDesktop: TGUID = '{75048700-EF1F-11D0-9888-006097DEACF9}';
var
  ActiveDesk: IActiveDesktop;
  ComponentsOpt: TComponentsOpt;
  hr: HRESULT;
  dwReserved: DWORD;
begin
  ZeroMemory(@ComponentsOpt, SizeOf(TComponentsOpt));
  ComponentsOpt.dwSize := SizeOf(TComponentsOpt);
  hr := CoCreateInstance(CLSID_ActiveDesktop, nil, CLSCTX_INPROC_SERVER,
    CLSID_ActiveDesktop, ActiveDesk);
  if SUCCEEDED(hr) then
  begin
    hr := ActiveDesk.GetDesktopItemOptions(ComponentsOpt, dwReserved);
    // ActiveDesk._Release; 
  end;
  Result := ComponentsOpt.fActiveDesktop;
end;