SDL_WINDOWID hack and fullcreen video problem

Hi,
I’m using SDLWINDOWID hack for my video player.
When changing to fullscreen, the call IDirectDraw2_SetCooperativeLevel() in
DX5_SetVideoMode() returns DDERR_INVALIDPARAMS.
If I use GetParent(SDL_Window) instead of SDL_Window for
SetCooperativeLevel(), no error returned, but video is not displayed.

Is there something wrong when passing the SDL_Window handle to
SetCooperativeLevel()?
How can this be done?

Thanks all~~–
?? Li Bo