Heh.  From what I know, internet sharing on a windows box is not the same as
packet forwarding.  It is actually NATing your packets - do a tcpdump to
verify.  This would mean that the box behind the w2k machine could get out
fine, but no one from the other side could reach it directly.  If  I
remember correctly, there used to be  "forward between interfaces" or such
option on NT, perhaps W2k has the same.  I checked on my box here and
couldn't find it, but that could be because it only has 1 interface.

-dallas