The DirectDrawEnumerate function enumerates the DirectDraw objects installed on the system. The NULL GUID entry always identifies the primary display device shared with GDI.
HRESULT DirectDrawEnumerate(
LPDDENUMCALLBACK lpCallback,
LPVOID lpContext
);
If the function succeeds, the return value is DD_OK.
If the function fails, the return value is DDERR_INVALIDPARAMS.
On systems with multiple monitors, this method enumerates multiple display devices. For more information, see Working with Multiple Monitors.