Search notes:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\instance name\Providers

This registry key stores the OLE DB Providers that SQL Server might use.
The names of the subkeys of this key are ProgIds that correspond to the list of providers that are shown in the SQL Server Management Studio in the Object Explorer under Server Objects -> Linked Servers -> Providers.
A new OLE DB Provider might be added with 
exec master.dbo.sp_MSset_oledb_prop N'Microsoft.ACE.OLEDB.12.0' , N'AllowInProcess'   , 1;
exec master.dbo.sp_MSset_oledb_prop N'Microsoft.ACE.OLEDB.12.0' , N'DynamicParameters', 1;
go
If such a provider has been added, it can be accessed for example with the T-SQL function openrowset.

See also

The subkey ProgID-of-an-OLE-DB-Provider
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Microsoft SQL Server\instance name

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