Changing Modes and Exclusive Access
Display modes can be changed using the IDirectDraw2::SetDisplayMode method. Modes can be changed by any application as long as all of the applications are sharing the display card.
The DirectDraw exclusive mode does not bar other applications from allocating DirecDrawSurfaces, nor does it exclude them from using DirectDraw or GDI functionality. However, it does prevent all applications, other than the one that obtained exclusive access, from changing the display mode or changing the palette.