Check out the new addition to the unsupported scenarios... http://www.microsoft.com/technet/isa/2004/plan/unsupportedconfigs.mspx#I nstallation ISA Server 2004 and ISA Server 2006 Should Not be Installed on a Domain Controller Problem: Installation of ISA Server 2004 on a domain controller is not supported unless the installation is performed as part of the Small Business Server 2003 Premium Edition Service Pack 1 installation, or the management wizards. Installing Isa Server 2006 on a domain controller or Small Business Server is not supported. Cause: Not supported. Solution: No workaround. Zippa-dee-do-dah, zippa-dee-ay! All mail to and from this domain is GFI-scanned.