var 
  hHookID: HHOOK; 

// function to make the menu transparent 
function MakeWndTrans(Wnd: HWND; nAlpha: Integer = 10): Boolean; 
type 
  TSetLayeredWindowAttributes = function(hwnd: HWND; crKey: COLORREF; bAlpha: Byte; 
    dwFlags: Longint): Longint; stdcall; 
const 
  // Use crKey as the transparency color. 
  LWA_COLORKEY = 1; 
  // Use bAlpha to determine the opacity of the layered window.. 
  LWA_ALPHA = 2; 
  WS_EX_LAYERED = $80000; 
var 
  hUser32: HMODULE; 
  SetLayeredWindowAttributes: TSetLayeredWindowAttributes; 
  i : Integer; 
begin 
  Result := False; 
  // Here we import the function from USER32.DLL 
  hUser32 := GetModuleHandle('USER32.DLL'); 
  if hUser32 <> 0 then 
  begin 
    @SetLayeredWindowAttributes := GetProcAddress(hUser32,'SetLayeredWindowAttributes'); 
    // If the import did not succeed, make sure your app can handle it! 
    if @SetLayeredWindowAttributes <> nil then 
    begin 
      // Check the current state of the dialog, and then add the WS_EX_LAYERED attribute 
      SetWindowLong(Wnd, GWL_EXSTYLE, GetWindowLong(Wnd, GWL_EXSTYLE) or WS_EX_LAYERED); 
      // The SetLayeredWindowAttributes function sets the opacity and 
      // transparency color key of a layered window 
      SetLayeredWindowAttributes(Wnd, 0, Trunc((255 / 100) * (100 - nAlpha)), LWA_ALPHA); 
      Result := True; 
    end; 
  end; 
end; 

// hook procedure 
function HookCallWndProc(nCode: Integer; wParam, lParam: Longint): Longint; stdcall; 
const 
 MENU_CLASS = '#32768'; 
 N_ALPHA = 60; 
var 
  cwps: TCWPStruct; 
  lRet: THandle; 
  szClass: array[0..8] of char; 
begin 
  if (nCode = HC_ACTION) then 
  begin 
    CopyMemory(@cwps, Pointer(lParam), SizeOf(CWPSTRUCT)); 
    case cwps.message of 
      WM_CREATE: 
        begin 
          GetClassName(cwps.hwnd, szClass, Length(szClass)-1); 
          // Window name for menu is #32768 
          if (lstrcmpi(szClass, MENU_CLASS) = 0) then 
          begin 
            MakeWndTrans(cwps.hwnd, N_ALPHA {Alphablending}); 
          end; 
        end; 
    end; 
  end; 
  // Call the next hook in the chain 
  Result := CallNextHookEx(WH_CALLWNDPROC, nCode, wParam, lParam); 
end; 

// Install the hook in the OnCreate Handler 
procedure TForm1.FormCreate(Sender: TObject); 
var 
  tpid: DWORD; 
begin 
  // Retrieve the identifier of the thread that created the specified window 
  tpid := GetWindowThreadProcessId(Handle, nil); 
  // The SetWindowsHookEx function installs an application-defined 
  // hook procedure into a hook chain 
  hHookID := SetWindowsHookEx(WH_CALLWNDPROC, HookCallWndProc, 0, tpid); 
end; 

// Stop the hook in the OnDestroy Handler 
procedure TForm1.FormDestroy(Sender: TObject); 
begin 
  if (hHookID <> 0) then 
    // Removes the hook procedure 
    UnhookWindowsHookEx(hHookID); 
end;