DirectDraw allows you to create off-screen surfaces in video memory that are wider that the primary surface. This is only possible when display device support for wide surfaces is present.
To check for wide surface support, call IDirectDraw4::GetCaps and look for the DDCAPS2_WIDESURFACES flag in the dwCaps2 member of the first DDCAPS structure you send with the call. If the flag is present, you can create video memory off-screen surfaces that are wider that the primary surface.
If you attempt to create a wide surface in video memory when the DDCAPS2_WIDESURFACES flag isn't present, the attempt will fail and return DDERR_INVALIDPARAMS. Note that attempting to create extremely large surfaces might still fail, even if the driver exposes the DDCAPS2_WIDESURFACES flag.
Wide surfaces are always supported for system memory surfaces, video port surfaces, and execute buffers.