It is known that Microsoft use Samba's code to teach their own progranners how SMB works. This is because their own code is such a hodge-podge of bugfixes on bugfixes. This is also the reason why Samba has been accused of optionitis over the years.
What I'm trying to lead up to is that Microsoft don't need to engineer incompatibilities between 98 and 2k: they have simpley acreted over time.
Wade.