Redirecting New Users and New Computers to a Specified OU

Either on you computer or on a domain controller run the below commands to make the changes.

To Redirect Users
C:\Windows\System32\redirusr DN_of_new_OU
For example:
C:\Windows\System32\redirusr ou=myusers,DC=mydomain,dc=com

To Redirect Computers
C:\Windows\System32\redircmp DN_of_new_OU
For example:
C:\Windows\System32\redircmp ou=mycomputers,DC=mydomain,dc=com

Note: Your domain functional level must be at at least Windows Server 2003.
If your DN contains spaces etc you will need enclose the DN with quotes.