This post explains how to list SQL Server Instances installed on the current server, using the Powershell Get-ItemProperty Cmdlet.
The Get-ItemProperty Cmdlet gets the properties of a specific item.
In this example, the command displays the Name and Data from the registry entries in the SQL registry subkey.Notice the Powershell drive : HKLM. It’s mapped to the HKEY_LOCAL_MACHINE .
Get-ItemProperty 'HKLM:\Software\Microsoft\Microsoft SQL Server\Instance Names\SQL'