Amazon is selling the upgrade version of Windows 8 Pro for £49 via Amazon's UK website. Customers who pre-order now now will receive a DVD-ROM containing the Windows 8 code and an installation key shortly after Windows 8's October 26 release date. See also: Windows 8 release date and features UK.

Update: Revealed: UK price for Windows 8 upgrade

This doesn't mean that Windows 8 Pro will retail for £49 in the UK. For one thing, the deal is for a DVD-ROM. We expect that most upgraders will be download Windows 8 direct from Microsoft and that will save on the cost of physical media and postage.

Also although the product manufacturer is Microsoft the vendor in this instance is Amazon. The online retail giant will be setting its own price. Microsoft will, in time, set a SRP for Windows 8, but cannot by law dictate for what price vendors sell it. It's possible that Amazon is hedging its bets here, getting into the market early with a deal it knows will be no cheaper than Microsoft's final UK price for Windows 8.

To that end, Amazon has made the following pledge in its 'Special Offers and Product Promotions' section: "Pre-order Price Guarantee: order now and if the price decreases between the time you place your order and the release date, you'll be charged the lowest price." Whether that means Amazon will match Microsoft's Windows 8 price remains to be seen.

Windows 8 UK price

We don't yet know the UK price for Windows 8. One of only two prices that Microsoft has revealed so far is the $39.99 it will charge US-based Windows XP-, Vista- and Windows 7-users to upgrade their PCs to Windows 8 Pro. That price, however, is valid only until January 31, 2013, or for about three months after the operating system's debut. We also know that upgrading from Windows 7 to Windows 8 a PC bought today will cost just £14.99 in the UK, subject to that offer being accepted at the time of purchase.

It is getting late in the day for Microsoft to announce its price for Windows 8, which launches 60 days from today and is already with manufacturers. We had the price for Windows Vista 58 days before it went to manufacturers, which was a whopping 148 days before it went on sale. Windows 7 pricing was made public 120 days before it hit the shops.

An upgrade from XP or Vista to Windows 7 Professional will set you back £189, but Microsoft will almost certainly set the Windows 8 price much lower. Pressure from Apple - which sells its OS X Mountain Lion for just £13.99, and a pressing need to disseminate it's new Windows Store to as many Windows users as possible are likely to make it an inexpensive upgrade.

For more on the changes in Windows 8 and how to use them visit Windows 8 Advisor. For detailed advice on installing Windows 8 Release Preview, read our article: How to install Windows 8.