>>6
Microsoft L2TP/IPSecのドキュメントを再度読んでみたところ、
FAQに
Q. Will this VPN client enable my computer to generate end-to-end IPSec traffic?
A. No. This VPN client establishes an end-to-end IPSec session between your computer and
the VPN server. It cannot establish an IPSec session with any other server for any purpose
other than L2TP traffic.
なんて書いているんで、Win9x同士でのエンドツーエンドIPSecには
使えないと思われ。