In order to keep what few vestiges of sanity I have left, I decided I would only be supporting Windows Authentication on a .NET Windows Forms app I've been developing for work. This meant firing up an Active Directory domain for testing.
Enter stage left - my PC with Loads-a-RAM, Quad Core CPU and Ubuntu 9.10 with Virtualbox 3.0.12.
Bish Bosh - and some fettling/googling later - I have a complete set of Windows 2003 Server VMs all running on my Desktop; a Domain Controller, a SQL Server 2005 Server, an IIS web server, and a Windows 7 client. They are networked together using an Internal network (software based within VBox itself) plus the DC is running a RAS NAT to the wired network for Interweb access.
Chuffin eck - it works really well. I bloody love Virtualbox - a complete test lab on a private LAN - on my desktop