Rename a SQL Server instance, a little catch
Can I rename an instance of SQL Server after I have already installed it on the computer? Simple answer is Yes and you can change the name of an instance as long as the server is not clustered.
There is a little catch between 2000 and 2005 version, by default when you change the name of the computer that is running SQL 2000 version, the new name is recognized during SQL Server startup. You do not have to run Setup again to reset the computer name. Still you have to update the SYSSERVERS system table by running the following procedure:
--For default instances
sp_dropserver old_name
GO
sp_addserver new_name, local
GO
--for Named instances
sp_dropserver old_servername\instancename
GO
sp_addserver new_servername\instancename, local
GO
Also http://support.microsoft.com/kb/303774 article completes the incomplete information from Books online "Server 2000 Books Online topic "Renaming a Server" is incomplete. The keyword "local" is missing from the example".
Nothing seems to worried with SQL 2005 though, refer to http://technet.microsoft.com/en-us/library/ms143799.aspx article for complete reference if you have such tasks to do.