When you create/open an ACCDB, Access 2007 uses the ACEDAO.DLL library which
supports the functionality you need for ACCDB. In code, VBA recognises this
as the DAO library.

When you create/open an MDB in Access 2007, it uses the DAO360.dll library
which supports the functionality appropriate for MDB. In code, VBA
recognises this as the DAO library.

You can verify this by opening the Immediate Window (Ctrl+G) and entering:
   ? References("DAO").FullPath

It doesn't make sense to try to use DAO360.dll for an ACCDB, since you would
run into trouble with the new things like complex data types listed at the
end of this article:
   http://allenbrowne.com/func-06.html