Search notes:

Registry: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\SQMClient

MachineId

In SQL Server, the value of MachineId can be queried like so: 
select
   value_data
from
   sys.dm_server_registry
where
   registry_key = 'HKLM\SOFTWARE\Microsoft\SQMClient' and
   value_name   = 'MachineId'

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