To clear up some confusion with Vista:
Upgrade version of Vistas:
Clean installs may be performed on all upgrades from Windows 2000/XP to Vista. Depending on the edition of your current OS and the edition you are upgrading to you may be able to perform an in-place upgrade. This handy table should make it clear what can be done.
32 and 64bit media:
Vista Ultimate comes with 32 AND 64bit DVDs in the retail package. For all other editions you may request the 64bit DVD or 32bit spanned CDs from this page for $NZD15 (Standard Delivery) or $NZD30 (Courier) this will take up to two weeks depending on your postage choice.