Via Microsoft
Short story: Any Windows 7 (bar W7 Starter Edition) equipped computers or laptops you buy within the next 6 months are automatically eligible for a $15 AUD upgrade to Windows 8 Pro Edition. Obviously, this offer is for purchasers of retail, pre-built computers, not beige-boxes which have been installed with OEM operating systems.
You must purchase a qualifying Windows 7 PC between 2 June 2012 and 31 January 2013 to be eligible for this offer. The last day to register and order your Windows 8 upgrade is 28 February 2013.
The Windows Upgrade Offer program is still not yet open, but you can head on to https://windowsupgradeoffer.com/en/ and put in your email address.
When the program opens, Microsoft will then notify you of it's availability.
Any additional information can be read in the Terms/Conditions and FAQ.
Offer Redemption
- Eligible customers must register for the Windows Upgrade Offer through this website by 28 February 2013.
- After customer registration and Microsoft validation, customers will receive a registration confirmation email.
- Upon the General Availability (GA) and release of Windows 8, customers will receive an email with a promotion code and instructions for purchasing and downloading the software.
- The promotion code will be redeemed during the upgrade ordering process to receive the promotional price.
- Customers will be able to purchase a downloadable version of Windows 8 Pro.
- An optional installation DVD is available for an additional fee, plus shipping and any applicable taxes or duties.
- Customers can also choose to create their own installation media on DVD or USB media after downloading Windows 8.