This is the registry library. The registry is basically a bunch of hives 
(HKEY_CURRENT_USER, HKEY_LOCAL_MACHINE, etc) that can be loaded from 
different places.

The various registry backends provide support for loading/saving specific types 
of hives:
 - ldb 
 - w95 (USER.DAT-style files)
 - nt4 (NTUSER.DAT-style files)
 - gconf (GNOME configuration)
 - rpc (Remote individual hives)

Instead of opening individual hives, one can also open a 'complete' registry by 
using one of these three functions:
 
 - reg_open_local() - load local registry, see below
 - reg_open_remote() - connect to remote registry over RPC
 - reg_open_wine() (not working yet)

reg_open_local() loads a set of hives based on smb.conf settings. 
Lines in smb.conf should have the following syntax:

registry:<hivename> = <backend>:<location>

So an example usage could be:

registry:HKEY_CURRENT_USER = nt4:NTUSER.DAT
registry:HKEY_LOCAL_MACHINE = ldb:tdb://registry.tdb

WERR_NOT_SUPPORTED will be returned for all hives that haven't been set.