>
> > For example a CreateRectRgnIndirect function works differently

with the

> same set of input rectangles in NT4 and in 2000. But nowhere in the

MSDN

> docs written that input rectangles must be specifically ordered.
>
> I disagree. left and right are surely ordered.
> Furthermore, 2000 is not a sp to NT4.

Of course, but I speak not about left and right.
The problem that consequent rectangles on NT4 must be in
left-to-right and top-to-bottom mode in the array. Else NULL will be
created.

Yes, this is not SP. But MS declared that GUI is OS-independenet.
And that's not true.