With SBS 2003 SP1 Premium, you also get ISA 2004 as an upgrade. A requirement is to uninstall the ISA 2000 Firewall client first. Someone asked whether you could use Group Policy to deploy the new Fireewall Client.
As usual, Chad Gross — our ISA man on the spot — had the answer:
How to Add Firewall Client via Group Policy:
If ISA is installed on SBS, then you’re going to want to be able to turn on
auto-detection as well: