Script to return the SQL Server service-account

--service_accounts.sql

-- return sql-server-service-account used by the default-instance
DECLARE @serviceaccount varchar(100)
EXECUTE master.dbo.xp_instance_regread
N'HKEY_LOCAL_MACHINE',
N'SYSTEMCurrentControlSetServicesMSSQLSERVER',
N'ObjectName',
@ServiceAccount OUTPUT,
N'no_output'
SELECT @Serviceaccount ServiceAccount_DefaultInstance

-- ditto for named-instance
DECLARE @serviceaccount2 varchar(100)
exec master.dbo.xp_instance_regread
N'HKEY_LOCAL_MACHINE',
N'SystemCurrentControlSetServicesMSSQL$sqlins01', -- edit
N'ObjectName',
@ServiceAccount2 OUTPUT,
'no_output'
SELECT @Serviceaccount2 ServiceAccount_NamedInstance

-- and for named-agent
DECLARE @agentaccount varchar(100)
EXECUTE master.dbo.xp_instance_regread
N'HKEY_LOCAL_MACHINE',
N'SYSTEMCurrentControlSetServicessqlagent$sqlins01', --edit
N'ObjectName',
@agentaccount OUTPUT,
N'no_output'
select @agentaccount ServiceAccount_NamedAagent