Registry writing and regisrty reading through SQL

In SQL server we have 2 undocumented stored procedures for reading from registry and for writing into registry. For reading from registry we use the xp_regread and for writing into registry we use xp_regwrite undocumneted extended stored procedures. These two SP`s can be found in master database of a particular server.

Usage :-
EXEC xp_regread @rootkey, @key,[@value_name],[@Value]
Example:-
EXEC master.dbo.xp_regread @rootkey='HKEY_LOCAL_MACHINE', @key='SOFTWARE\Microsoft\Microsoft SQLServer\80\Replication\Subscriptions\',
@value_name= 'SubscriberEncryptedPasswordBinary'

EXEC xp_regwrite @rootkey,@key,@value_name,@type,@value
Example:-
EXEC master..xp_regwrite @rootkey='HKEY_LOCAL_MACHINE', @key='SOFTWARE\Test',
@value_name='TestValue', @type='REG_SZ', @value='Test'