Void CaptureScreen(HWND hCaptureWnd)
{
   int nScreenWidth = GetSystemMetrics(SM_CXSCREEN);
   int nScreenHeight = GetSystemMetrics(SM_CYSCREEN);
   HDC hDC = GetDC(hCaptureWnd);
   HDC hCaptureDC = CreateCompatibleDC(hDC);
   HBITMAP hCaptureBitmap =CreateCompatibleBitmap(hDC, nScreenWidth, nScreenHeight);
   SelectObject(hCaptureDC,hCaptureBitmap);
   BitBlt(hCaptureDC,0,0,nScreenWidth,nScreenHeight,hDC,0,0,SRCCOPY);
   
   // w tym miejscu musisz zapisac plik z HBITMAP hCaptureBitmap

   ReleaseDC(hCaptureWnd,hDC);
   DeleteDC(hCaptureDC);
   DeleteObject(hCaptureBitmap);
}