First things first: get the new Vista install on the domain.
I run a Windows Active Directory domain at home, including an Exchange server. This works nicely when you host your own domain, and also comes in really handy for learning things that you'd never be able to "play with" at work due to time or other constraints (like Vista!).
Unfortunately, this was my first stumbling block. Adding a machine to the domain under XP and earlier is pretty straightforward, but it's pretty easy to get distracted by all the "eye candy" in the OS, not to mention the frequent popups as Vista discovered updates to components in my system (this will become a frequent issue as I have discovered...).