A simple registry fix is all it takes
While making a routine check of an application log, I noticed the warning The configuration of the SQL instance MSSQLSERVER is not valid. On this test machine, I previously uninstalled the default MSSQL instance, which is typically named MSSQLSERVER. To get an idea of the frequency of this warning, I filtered the application log by selecting Action on the Event Viewer's menu bar, choosing Filter Current Log, and selecting SQLBrowser in the Event sources drop-down list (see Figure 1). I discovered that the SQLBrowser warning was a daily event, as Figure 2 shows.
Related: DBAs and SQL Server Logs
I checked the file system to make sure no remnants existed from the MSSQLSERVER instance that I previously uninstalled. No remnants were present, so I fixed the problem by editing the registry. If you run into this problem, here's how you can fix it:
1. Open regedit.exe and export the entire HKLM\SOFTWARE\Microsoft\Microsoft SQL Server registry key as a backup.
2. Navigate to HKLM\SOFTWARE\Microsoft\Microsoft SQL Server in the registry.
3. Highlight the Microsoft SQL Server key.
4. Double-click the InstalledInstances entry in the Name column.
5. In the Edit Multi-String dialog box, which Figure 3 shows, double-click MSSQLSERVER (if that's your tombstoned instance) and press the Delete key on your keyboard. Note that in Figure 3, there's a valid, currently installed instance named TEST listed in addition to the non-existent MSSQLSERVER instance. In your environment, you might have different instances listed or no other instances listed besides MSSQLSERVER in the Edit Multi-String dialog box.
6. Click OK to exit the Edit Multi-String dialog box.
7. Navigate to HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\Instance Names\SQL.
8. Highlight the SQL key and look for your tombstoned reference (e.g., MSSQLSERVER) in the Name column. In my case, there wasn't a tombstoned reference. If your installation has one, delete it by highlighting it, right-clicking, and selecting Delete.
9. Navigate to HKLM\SOFTWARE\Microsoft\Microsoft SQL Server\MSSQLServer.
10. Highlight the MSSQLServer key (which will include a Current Version subkey) and press the Delete key on your keyboard.
11. Close regedit.exe.
About a week after performing these steps, I opened the application log again, filtered it, and looked for the SQLBrowser warning. There were no new occurrences of this warning. The registry fix solved the problem.
Learn more from my articles "Disable Video ActiveX Controls in Internet Explorer on the Fly" and "Fix for Double Vision in Disk Utilities."