When you attempt to register the SPN (Service Principal Name) using the Setspn utility, you will receive an error if the NetBIOS name of the computer where SQL Server 2000 is running is different from the domain name if the NetBIOS name of the computer where SQL Server 2000 is running is different from the domain name, when using the following syntax:
setspn -A MSSQLSvc/Host:port serviceaccount
The error will look similar to:
Registering ServicePrincipalNames for (null)
Failed to assign SPN to account '(null)', 0x57
setspn -A MSSQLSvc/JSI007.JSIINC.COM:1433 JSIINC/SQLAccount
JSI007 is the host name of the SQL Server.
JSIINC is the Windows domain name.
SQLAccount is the SQL Server domain account under which SQL Server service is running.