Sometimes, even though you change the settings of your instance name in SQL 2005 Management Studios, there are still references to the old name that you don’t know where to change.
First, you will need to see what the actual instance name is. To get this, execute the following query in SQL Management Studios — sp_helpserver.
Copy that instance name and insert the old instance name and the name you want to change it to in the following query —
exec sp_dropserver ‘old servername’
exec sp_addserver ‘new servername’, ‘local’
Finally, execute that entire string. Then, to verify, run sp_helpserver again to see your new instance name.