Uninstall a single SQL server Instance through the registry

Question

I'm running SQL Server 2014 and have 50 separate instances running. This is the max limit of number of instances for this version and I obviously need to uninstall some instances and clean up.

However upon research there's a bug which won't allow you to uninstall instances through the Programs and Features installer or command line when you have 50 instances installed. The installer freezes when querying the list. I checked the bootstrap log files and the exported errors state that it can't perform the operation because there are too many instances which is the whole problem in the first place!

I need to uninstall the instance through the registry. I was able to remove the instance from HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall using msiexec but when I did that the SQL Browser service crashed, the other sql instances lost connection and the services for the old instance would reappear. I had to restore the registry from the backup I made. Is there a way to remove an instance from the registry properly and re-situate the browser service? Maybe some registry items I'm missing?

Answer 1

I've figured out the solution for this based on an order of operations. This resolved my issue.

• Stop the SQL Browser service
• SC Delete the SQL Server service for the particular erroneous instance
• Run the uninstall command from the setup.exe using the installer disk Setup.exe /Action=Uninstall /FEATURES=SQLEngine /INSTANCENAME=MyInstance /Q
• (The SQL Server Agent service for the erroneous instance will disappear)
• Start the SQL Browser service
• Uninstall subsequent erroneous instances through Programs and Features as this will now complete without hanging.