Just in case you missed a warning on Microsoft's Knowledge Base last week, be aware that its Internet Connection Firewall and its Basic Firewall do not block Internet Protocol Version 6 traffic.
And that this applies to:
Microsoft Windows Server 2003, 64-Bit Datacenter Edition
Microsoft Windows Server 2003, 64-Bit Enterprise Edition
Microsoft Windows Server 2003, Datacenter Edition
Microsoft Windows Server 2003, Enterprise Edition
Microsoft Windows Server 2003, Standard Edition
Microsoft Windows Server 2003, Web Edition
Microsoft Windows XP 64-Bit Edition Version 2003
Microsoft Windows XP 64-Bit Edition Version 2002
Microsoft Windows XP 64-Bit Edition Version 2002 SP1
Microsoft Windows XP Home Edition
Microsoft Windows XP Home Edition SP1
Microsoft Windows XP Media Center Edition
Microsoft Windows XP Professional
Microsoft Windows XP Professional SP1
Microsoft Windows XP Tablet PC Edition
But don't worry. Microsoft is recommending that you buy other firewall software that can filter and block IP version 6 traffic.
It rather charitably describes this as a "workaround".