In-Place Upgrade failure from SQL Server 2008 SP1 to SQL Server 2008 R2

Recently I was trying to upgrade SQL Server 2008 to SQL Server 2008 R2. The upgrade failed with error message below.

TITLE: Message Details

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The Instance ID ‘MSSQLSERVER’ is already in use by SQL Server instance ‘MSSQLSERVER.INACTIVE’. To continue, specify a unique Instance ID.

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BUTTONS:

OK

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Brief Background of upgrade process:

Here we have an orphaned SQL instance named MSSQLServer.Inactive. Let’s understand the upgrade process here. During your upgrade, there are two stages:

Pre-PointOfNoReturn

Post- PointOfNoReturn

Point of No Return is a point at which 2008 R2 will take over the instance name and SQL Server 2008 will be then uninstalled.

Resolution:

In this scenario, the setup is failing at Pre-Point Of No Return otherwise we would have tried to repair the SQL Server 2008 R2 instance.

The first thing I tried was renaming the registry key (below) and upgrading it, but it did not help this time (this has helped in some cases)

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL\Inactive

The second option is to remove the existing instance and reinstall a fresh default instance.

I tried to  uninstall the new SQL Server 2008 R2 instance from ADD/REMOVE Programs, but it was not showing the instance name as it was inactive.

Ran below command

setup /action=uninstall /instanceid=MSSQLSERVER  /features=SQLEngine,Replication

(You can select more features if it is installed in your environment. Refer Summary.txt for last upgrade failure)

After the uninstall was successfully completed, I was able to install the SQL Server 2008 R2 instance.