IsAvailable Example for C++ 5.0 and later

   BOOL bRet; 
   ILEADRasterTwain *pltRasTwain; 

   ::CoCreateInstance(CLSID_LEADRasterTwain, NULL, CLSCTX_ALL, IID_ILEADRasterTwain, void **)&pltRasTwain);

   bRet = pltRasTwain->IsAvailable ((long)m_hWnd);
   if (bRet) 
      MessageBox(TEXT("Twain is installed"));
   else
      MessageBox(TEXT("Twain is not installed"));