renaming a SQL Server with installed named instances [closed]

Question

We have a hosted server that is named, by the hosting company, as something like WinEnt99. We would like to rename it to something more meaning like OurMonitor1.

We have already installed a few instances of SQL Server 2008 R2.

Is there anything that we need to (re)configure in SQL Server / SSMS ?

I have an application that was reading the database settings from the registry, and connecting the database fine. Now, it won't connect to the database. The only thing that I can think of is that we renamed the server last week sometime.

EDIT 02 Oct 2012:- The Server is being renamed. The named instances are not.

I've run

sp_helpserver
select @@servername

Which showed the old server name, and

sp_dropserver 'Old Server Name\Instance_name'
go
sp_addserver 'New Server Name\Instance Name','local'
go

Then confirmed the details in

sp_helpserver
select @@servername

Answer 1

First collect the output of the current instance configuration. You can get the instance name stored in the SQL Server metadata.

Make sure you have backup of all the database if you are changing the production server instance name.

sp_helpserver
select @@servername

You can change the instance name using below query. Default Instance

sp_dropserver 'old_name'
go
sp_addserver 'new_name','local'
go

Named Instance

sp_dropserver 'Server Name\old_Instance_name'
go
sp_addserver 'ServerName\New Instance Name','local'
go

Verify sql server instance configuration by running below queries

sp_helpserver
select @@servername

Restart the SQL Server Services.

net stop MSSQLServer
net start MSSQLServer

[Update]

You cannot change connection instance name as this action is not supported. Only option is re-install SQL server. See answer in MSDN here