Microsoft Australia has admitted that Windows 8 will only be available as an upgrade for existing customers who have previous versions of the operating system running on their PCs.

Those who have Windows XP, Vista, or 7 installed can purchase Windows 8 Professional in a box for $69.99 through retailers, or as a digital download for $39.99 via Microsoft's website.

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Harvey Norman, which held its traditional Windows midnight launch, is currently selling Windows 8 Pro for $58. JB Hi-Fi is running the same deal.

A full version of the product is not available, nor did Microsoft state whether and when it will be.

While Windows fans may not be put at a direct disadvantage, Microsoft may have trouble attracting new customers who will be forced to purchase a previous version before they are able to install Windows 8.

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