Renaming your ISA server is now a supported process, as follows:
On the ISA Server 2004 computer, click Start, right-click My Computer, and then click Properties.
In the System Properties dialog box, click the Computer Name tab.
On the Computer Name tab, click Change.
In the Computer Name Changes dialog box, enter the new name in the Computer Name field, and click OK.
Click OK in the Computer Name Changes dialog box informing you that you must restart the computer before the changes take effect.
In the System Properties dialog box, click OK.
In the System Settings Change dialog box, click Yes to restart the computer.
Be aware of other systems that may refer to the ISA Server name. For example, you may need to change the ISA Server name on manually configured firewall clients, or change the name of the ISA server in any scripts you created.