Your computer should already be set to Australian Dates and Times, however some resellers forget to do this, and your computer defaults to American date formats (mm/dd/yyyy).
Click Start
Settings
Control Panel
Regional Settings (or Regional Options)
Note: With Windows XP, you may need to click "Classic View" to see the standard control panel applications
Check to make sure your location is set to English (Australia)
If not choose English (Australia) via the drop down box.
Click OK