Howtogeek posted a tutorial about making Windows Home Server into a Domain Controller

Active Directory lets companies manage users, computers, printers, and more from a centralized location. Have you wanted this functionality at home but don't have money for Windows Server? Here's how you can promote Windows Home Server to a domain controller.
Maybe you don't have 100+ computers in your closet but sometimes it may feel that way. Active Directory allows you to centrally manage the users that can log into the machines as well as help quickly set up machine preferences and can even help manage your virtual machines. If you have been wanting a better way to manage it all, or even just want to dive into Active Directory here's how you can do it on the cheap.
Please be aware that Microsoft specifically says you are not allowed to do this according to their end user license agreement (EULA) that you have to agree to when installing or setting up a Windows Home Server. As such, this article will be strictly for educational purposes.

  How To Make Windows Home Server into a Domain Controller