Microsoft's Nathan Mercer told me this is a special build - the laptops are so new he had to create an image with fresh drivers, plus a full Tech.Ed user experience. This also includes New Zealand-flavoured wallpapers and other customisations.
The laptops also come with the latest Microsoft Office 2010 CTP.
If you are not getting these laptops but still would like to have the New Zealand-based theme, it looks like this will be released for download in October when Windows 7 becomes available for consumers.
Also if you didn't take the offer, you still have a chance to leave Tech.Ed NZ 2009 with one of those: Microsoft is running a competition lasting the three days of Tech.Ed. There seven laptops to be given away, and to be in the draw you have to fill a form with answers to seven puzzles. These answers will be around Tech.Ed NZ 2009 somewhere. Entry forms are available when you collect your badge.
Other related posts:
Registrations open for Microsoft Tech.Ed New Zealand 2010
Connect with your local .Net user groups
Microsoft Tech.Ed Online: Office and UC