Configuration Manager requires a dedicated SQL Server instance

In my lab environment I’m doing quite a lot of ConfigMgr testing. Recently, I was doing some testing on System Center Configuration Manager and Endpoint Protection (current branch – version 1511) and I broke the ConfigMgr primary site server and decided to re install the primary site.

In my lab I am using a dedicated SQL 2014 server to host the database and a dedicated server for the ConfigMgr installation. So I uninstalled the site server VM using the uninstall wizard, I deleted the database file in SQL and started a new installation wizard.
During the installation, the prerequisite checker gave me the following error. The error message stated that the SQL instance chosen already has a site database.

Configuration Manager requires a dedicated SQL Server instance to host its site database. You selected a SQL Server instance that hosts the site database for another Configuration Manager site. Select a different SQL Server instance for this new site to use, or resolve the conflict by uninstalling the other site or moving its database to a different SQL Server instance.

To solve this problem, I logged on the SQL Server and started the registry editor, there I found the following registry key with information about the ConfigMgr site:

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SMS]

After removing the registry key and restarting the SQL server I was able to continue the new ConfigMgr installation.

Kind regards,

Pouyan