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:

setspn -A MSSQLSvc/JSI007.JSIINC.com:1433 SQLAccount

Registering ServicePrincipalNames for (null)

        MSSQLSvc/JSI007.JSIINC.com:1433

Failed to assign SPN to account '(null)', 0x57
To workaround this behavior, use the following syntax:
setspn -A MSSQLSvc/Host:port domainname/serviceaccount

like:

setspn -A MSSQLSvc/JSI007.JSIINC.COM:1433 JSIINC/SQLAccount

Where:

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.
NOTE: The NetBIOS computer name of the SQL Server where the SPN is being registered is NOT JSIINC.