Curious About SQL Server Registry Entries
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  I have noticed that several of my SQL servers don't have the required registration data saved within the registry. 


SQL server will have everything in the registry settings. For shared Features, I believe the registry is HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Installer\UserData\S-1-518\Components\0D1F366D0FE0E404F8C15EE4F1C15094

Refer to File Locations for Default and Named Instances of SQL Server