Changing IP adress on ISA 2004

I have an ISA 2004 server with two NIC's. One NIC is facing the internal
network and the other is facing the Internet and has public IP adresses
associated with it.

Now I need to change the public IP adresses because of some changes we are
making to our network. How do I do this in the proper fashion? I have never
actually installed an ISA server, so I am unaware of how the IP adresses
gets associated with the NIC's. My worry is that if I change the IP numbers
on the NIC from within Windows 2003, then the ISA configuration will be
destroyed. Any advice?

Thanks in advance

Rasmus Kromann