系统服务程序弹出对话框

BOOL ShowMSGBox(string msg, string cap)
{
 try
 {
  int sessionId = WTSGetActiveConsoleSessionId();
  DWORD result = 0;
  BOOL bSuccess = WTSSendMessage(WTS_CURRENT_SERVER_HANDLE, sessionId, (char*)cap.c_str(), cap.size(), (char*)msg.c_str(), msg.size(), MB_OK|MB_ICONEXCLAMATION, 0, &result, true);
  return bSuccess;
 }
 catch(exception& e)
 {
  oLogWrite.WriteToLog(e.what());
  return FALSE;
 }
}

但上述方法在操作系统启动时，有时无法弹出所需对话框