Alejandro85 said:
Windows 7 Professional (or even Ultimate) isn't going to help you. ...

There you can enable the role of "domain controller" to create the domain and start playing with it.
There is a 180 days trial here:
Alejandro, I cannot thank you enough. Exactly what I need. I had the feeling I was missing something and would have found out after upgrading - you have really helped me a lot. THANK YOU!