samba - Mar 2008 - net command - createcomputer parameter

How can I find the correct path of the ou?
When I di this: net ads join 
createcomputer="Servers/Windows/Computers/AD test" -U Administrator

I receive the following error:
Administrator's password:
Failed to pre-create the machine object in OU 
createcomputer=Servers/Windows/Computers/AD test.
Failed to join domain: No such object