When I moved the SBS 2003 over to the (unsupported) HyperV platform, one of the things I had to do was to uninstall ISA 2004 and take the virtualized box back down to one nic.
Just a reminder of the steps I took — this is from the SBS 2008 migration checklist:
c Uninstall ISA Server 2004. If ISA Server 2004 is installed on the server running SBS 2003, you must uninstall it before you can begin the migration.
c Uninstall the ISA Server 2004 desktop client. To uninstall the ISA Server 2004 desktop client, follow the instructions in this blog post (http://msmvps.com/blogs/kwsupport/archive/2008/09/07/uninstalling-isa-2004.aspx).
c Export your third-party SSL certificates. If you have any third-party SSL certificates installed on the server running ISA Server 2004, you should export the certificate for reinstallation on SBS 2003.
c Uninstall ISA Server 2004. Uninstall ISA Server 2004 from Control Panel using Add or Remove Programs.
Import your third-party SSL certificates. Once you have uninstalled ISA Server 2004 you will need to import your third-party SSL certificates onto the server running SBS 2003. To import your certificates, follow the instructions starting with the section “Installing the SSL Certificate into IIS” in this blog post (http://blogs.technet.com/sbs/archive/2007/08/21/how-to-install-a-public-3rd-party-ssl-certificate-on-iis-on-sbs-2003.aspx).
I also relied on Chad Gross’s “killing off ISA” blog post here:
Killing off ISA – Aimless Ramblings from a Blithering Lunatic . . . – MSMVPS.COM:
One setting I noticed that needed to be updated (especially if you removed the ISA a week or two before you did the rest of the migration was/is to remove the proxy ISA server settings from inside WSUS server proxy settings. If you leave that proxy server information behind inside of WSUS, your WSUS server won’t sync up to get patch information.