I would suggest to use a Windows 7 host and the Openvpn tun driver (the only one that did install on x64 windows in any case). Windows XP IPv6 stack is lacking as compared to the one in Vista and 7 (no support for statefull DHCP is one of the lacking features). also I would want to use Vista/7 firewall instead of the one in XP :) I do see that the Win7 machine has a default gateway (your XP machine's link local address). You could simply configure your 7 machines manually: netsh int ipv6 add route prefex::/64 11 store=persistent netsh int ipv6 add route ::/0 11 router ipv6 address store=persistent where 11 is the IDX, obtained through netsh int ipv6 show int. It might be worhtwhile to disable the firewall on the XP machine, as surely it should be pingeable by the other machines.

Pity it does noet work as I was planning on doing exactly that: routing a subnet with an AYIYA tunnel ending on a Windows XP system. Any chance this will be fixed in the foreseeable future?