HDC hDCScreen = GetDC(NULL);
  int horres=GetDeviceCaps(hDCScreen,HORZRES);
  int vertres=GetDeviceCaps(hDCScreen,VERTRES);
  int freq=GetDeviceCaps(hDCScreen,VREFRESH);
  ReleaseDC(NULL, hDCScreen);
  horres=1024;
  vertres=768;
  DEVMODE dm;
  ZeroMemory(&dm, sizeof(DEVMODE));
  dm.dmSize = sizeof(DEVMODE);
  dm.dmPelsWidth = horres;
  dm.dmPelsHeight = vertres;
  dm.dmDisplayFrequency = freq;
  dm.dmFields = DM_PELSWIDTH | DM_PELSHEIGHT | DM_DISPLAYFREQUENCY;
  ChangeDisplaySettings(&dm, 0);