I've looked through most of the startup scripts, and I came across what I think launches the first boot configuration program. To run it directly enter "sudo /usr/sbin/oobe", though I don't know if having the full desktop loaded when you run it will cause any problems, or you could delete the file it checks to see if it has been run before "sudo rm /usr/share/oobe/oobe.log" and it should then run the first boot configuration program when you reboot.
Note, I haven't actually tested this for myself, but I think it will work.