The ISA Server 2004 firewall can be configured to use strong, two-factor authentication to allow VPN clients access to selected network resources. When two-factor authentication with smart cards and the ISA Server 2004 firewall's stateful packet and application layer inspection engines kick in, you know you've got the best Firewall/VPN device you can get. Idan Plotnik shows you how to make it happen.
 
Implementing ISA Server 2004 2004 PPTP VPN based Smart Card EAP and RADIUS Authentication without Making the ISA Server 2004 Firewall a Domain Member by Idan Plotnik