The latest preview build of Windows 10 includes a preliminary version of Cortana, the voice recognition technology that first debuted on Windows Phone. However, if you're in Australia the chance is you won't see it.
As a recent blog post from Microsoft reminds us, right now Cortana only works if you're using US English. You can change your region and language settings to test it, but as we learned with the phone version, US-centric builds don't work well with an Australian accent.
On Windows Phone, there was a three-month gap before an Australian Cortana build appeared; hopefully there will be a similar gap before we see it on the Windows 10 desktop.