I've solved the problem to change DelphiX's originality:
In DXDraws.pas there is a function like this:

function TDirectDrawSurface.GetBitCount: Integer;
begin
Result := SurfaceDesc.ddpfPixelFormat.dwRGBBitCount;
end;

and I changed it like this:

function TDirectDrawSurface.GetBitCount: Integer;
begin
Result := 8;
end;

Thank you for your reply holybyte...