Microsoft hit a home run with their NT Domain methodology... Then the Internet started to "take ownership" of the "Domain Model" so Microsoft updated Windows 2000 with DNS level controls in their new Active Directory Domains..
All fine and dandy unless you really want a secure system and you didn't even want to Mix the Internet with your "office space"... It works, but it seems to need 3 servers to trust it and make sure it works.
Windows 2003, then Windows 2008 Servers all had their improvements and complications, but in my experience they also add complications to the management of a small system (and also cost). For me the domain needs to be about defining the network and getting some work done. It is not about getting a 3 level certification in IT protocols blessed in orthodoxy.
Recently I have started testing a Samba (Ubuntu based) Domain Controller that emulates the NT Domain on a Linux Stack. So far, pretty good.. Fast performance and reliable. In the end it is something else to learn If I really want to stick to it. That said, I pushed go, got it turned on, have attached 3 computers to the Domain and its been running for a week without any problems.
The important part is that it is being developed and continued by an active group (unlike MS NT , Win2K at MS.. in factwhy don't they open source NT?).. I have a Win2008 Server running in the Samba Domain just for comparison. The beauty of this is that about anything including Win2007 and my Windows 7 Machines can join the Samba Domain. My Windows NT Domains are not so friendly w/ Windows 7. Still, I get the simplicity of a simple domain structure that I grew to appreciate on the old NT Model.
There are many things to learn in life. One I am hoping to learn is not to spend too much time on Microsoft systems that will be thrown away before I am actually done using them. Putting Terminal CAL's on that 2008 Server is not something I am running to spring for either, though this may be one of the only arguments for not jumping ship entirely.
Try the Samba Domain controller: A good one is http://www.turnkeylinux.org/domain-controller:
