Windows 8 has passed the first milestone on its way to retirement after Microsoft ended retail sales of the operating system.

As of 31 October, retailers will no longer be able to order more Windows 8 to sell beyond their existing stock, although it can still be bought installed on a new PC. The operating system went on sale just over two years ago on 26 October 2012, and Microsoft is already shifting emphasis to Windows 10, expected in the middle of next year.

No date has yet been set for when sales of Windows 8 via manufacturers will end — and Microsoft has said it will continue to support the operating system until January 2023. Windows 8.1 is still available at retail and no date has been set for the end of sales yet.

Windows 8 was a significant departure from the classic Windows look and feel, bringing in a new tiled start screen that met with considerable opposition from businesses worried about having to retrain staff to use the new interface.

As such, probably of more significance to business users is the news that some versions of Windows 7 are now no longer available to buy installed on new PCs from manufacturers.

Also as of Halloween, Windows 7 Home Basic, Home Premium, and Ultimate are no longer be available to buy installed on PCs, according to Microsoft. In reality, as manufacturers and retailers still have large stocks of Windows 7 PCs, it will be some time before they become scarce.

Sales of Windows 7 Professional will continue and Microsoft has said it will give a year's notice of the end of sale date. As the end of mainstream support for Windows 7 is due in January next year, it may mean, as Larry Seltzer argues elsewhere on ZDNet , that Microsoft will end up extending mainstream support for Windows 7.

Also, it's worth noting that enterprise customers with volume licensing deals can still 'downgrade' to previous versions of the operating system they have licensed.

And of course, although Microsoft would be very happy to see customers moving to the latest versions of its operating system, users tend to move at a much slower pace. According to figures from NetMarketShare, Windows 8 and 8.1 together account for 16.8 percent of PCs connecting to the web, while Windows 7 has 53 percent of the market. The antique Windows XP still holds onto 17.2 percent market share.

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