This problem can occur if the Remote Registry service on the domain controller that holds the schema master role in the forest does not run.
The ISA Server 2000 Enterprise Initialization tool can modify the Windows 2000 Active Directory schema if the tool connects to the domain controller that holds the schema master role, and then locates the following registry value:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Ntds\Parameters\Schema
Update Allowed
If the value is set to
1 (true), ISA Server 2000 does not modify the value.
If the value is set to
0 (false), ISA Server 2000 changes the value to
1,
makes the schema modifications, and then changes the value back to
0.
NOTE: The error will also occur if the Network Interface cards in the machine have been disabled.