Hello Adrian,
the international version 9.2 does not work with any version of Vista due to many problems, you will have to wait until the international version of Pro X is avaiable. At the moment we are translating the german version Pro X into english, but at least I think there will be not publication until the fourth quarter of this year. My main problem (I am translating the manual) is the amount of pages in the manual (560 pages), this needs a lot of time, because I do this beside my regular job in my free time.
I do not know the situation in Australia, here in Germany normally most of the "bundled" complete pc systems include Vista, but if you talk to the dealers you have in most cases the possibility to get XP instead of Vista. I buyed for my family two new computers in the last week, both with XP Pro. At the moment I would always prefer XP, because it needs much less ressources than Vista and offers a better compatibility to programs and hardware.
Best wishes
Markus