From Bob on the ISAserver.org Message boards at: http://forums.isaserver.org/m_2002009437/mpage_1/key_/tm.htm#2002009650
Ok...I have seen a few dead threads about Upgrading the client.
Here are the two scripts to first uninstall the ISA 2000 client and then install the ISA 2004 client.
Uninstall ISA 2000 client:
msiexec /x \\<isa2000 computer>\mspclnt\MS_FWC.MSI /quiet /norestart
Install ISA 2004 client:
msiexec /i \\<isa2004 computer>\mspclnt\MS_FWC.msi /quiet
We have Auto Detect running and I think the only issue is that the web proxy settings do not get updated until the computer is rebooted. If you really wanted to, you could force a reboot with the second script by using the /forcerestart.
Thomas W Shinder, M.D.
MVP -- ISA Firewalls