Join a computer to AD DS with Built-in Domain Guest

Hi,

I am using an AD DS server on Windows 2008 r2.

It is only a test server so there are no security concerns. Any method will do.

So far I managed to get members of Domain Guests to join a computer without problems.

However the same settings don't seem to work on the built-in Guest account.

Even a user copied from Guest will be able to do the join, but not the built-in account.

What could prevent the built-in group to do this, and how can it be bypassed?

Also, is it possible to allow ANONYMOUS LOGON to join a computer?

Thank you.