function TaskmanWindow: HWND;
type
  TGetTaskmanWindow = function(): HWND; stdcall;
var
  hUser32: THandle;
  GetTaskmanWindow: TGetTaskmanWindow;
begin
  Result := 0;
  hUser32 := GetModuleHandle('user32.dll');
  if (hUser32 > 0) then
  begin
    @GetTaskmanWindow := GetProcAddress(hUser32, 'GetTaskmanWindow');
    if Assigned(GetTaskmanWindow) then
    begin
      Result := GetTaskmanWindow;
    end;
  end;
end;

procedure ShowTaskmanWindow(bValue: Boolean);
var
  hTaskmanWindow: Hwnd;
begin
  hTaskmanWindow := TaskmanWindow;
  if hTaskmanWindow <> 0 then
  begin
    ShowWindow(GetParent(hTaskmanWindow), Ord(bValue));
  end;
end;


Beispiel:  ShowTaskmanWindow(False);