Microsoft early today began feeding Windows 8.1 to customers already running Windows 8, making good on a bold promise to pick up the pace on the development and release of its flagship client operating system.

Shortly after 7 a.m. ET, Microsoft posted the free Windows 8.1 update to its Windows Store, the official distribution channel for the tile-based apps that have been a hallmark of the new OS.

Customers were alerted to the update's availability when they reached the Windows Store. "You can keep working while the update is downloading," the Windows 8.1 screen stated. "We'll let you know when it's time for the next step."

That was a good move, as Windows 8.1 weighed in at just over 2.8GB. On slower connections, the download could take hours.

Computerworld began updating several instances of Windows 8 when Microsoft made the update available, and encountered no significant issues. Downloads were slow, but not significantly so, and did not appear bogged down by overloaded servers, as is often the case with other operating system updates and upgrades, such as the annual iOS refreshes from Apple.

Microsoft will launch retail packaging for Windows 8.1 -- suitable for those who may want to upgrade from Windows 7 or perhaps even an older OS -- tomorrow. The Redmond, Wash. company will not discount the upgrade this time around, as it did a year ago when it launched Windows 8. Prices for the upgrades will be $120 for Windows 8.1 and $200 for Windows 8.1 Pro.

Also scheduled for Friday: Other OEMS' new PCs, tablets and 2-in-1 devices powered by Windows 8.1 and its scaled-back sibling Windows 8.1 RT.

Microsoft will start selling its in-house Surface line of Windows 8.1 tablets next Tuesday at prices beginning at $449 for the Surface 2 and $899 for the Surface Pro 2.

While Windows 8.1 includes a host of enhancements and new features, it's also a second crack at the OS, which was widely disparaged by reviewers and customers when it debuted last year. Many of the changes contained in Windows 8.1 are reactions to customer complaints, including a partial restoration of the iconic Start button and an option that lets people who want to avoid the tile-style user interface (UI), once called "Metro," by booting straight to the traditional desktop.

For businesses, however, the biggest change is not in the code, but in the faster release cadence that Microsoft promised, and then delivered on today.

While the company has not publicly confirmed that it will update Windows annually, most analysts expect it to do so. And that accelerated tempo -- three times faster than previously -- has enterprises concerned, say experts.

"There's a good chance that enterprises will stay on Windows 7 as long as possible," said Gartner analyst Michael Silver in an interview last week, talking about corporations' reaction to Windows 8's faster cadence.

Microsoft today launched the long-awaited Windows 8.1 update, once code-named "Blue," as a free download for current users of Windows 8 and Windows RT.

The problem rests not only with the quicker pace but also with Microsoft support policy, which starts a countdown clock for Windows 8 today. Two years from now, Microsoft will stop supporting the original Windows 8, halting security patches and other fixes. To continue receiving such updates, customers must update to Windows 8.1.

The combination of a shorter release cycle and the support restrictions means that companies which want to keep up with Microsoft will essentially have the next 12 months to test Windows 8.1 and uncover and remediate any application compatibility problems, then another 12 months to deploy the OS.

That's a staggering change from current practice, where corporate IT not only takes much longer stretches to test and deploy, but is leery of change as it inevitably costs money and consumes resources.

Microsoft's changes will drive most businesses to ignore Windows 8, perhaps even its successor, and instead standardize on 2009's Windows 7, which most firms have already deployed, Silver said. In turn, that means Windows 7 will probably follow in Windows XP's footsteps, not only becoming the default PC operating system but also one that corporations will be very hesitant to abandon, even as it approaches its retirement of early 2020.

Redmond backed itself into a corner with its radical overhaul of Windows last year and its continued commitment to the Metro UI as evidenced in this year's Windows 8.1, which left the conventional desktop mode nearly untouched. With enterprises unlikely to bother deploying Windows 8.1 to large numbers of workers, they have little reason to purchase new touch-enabled PCs and can instead throw that money at tablets, smartphones and the occasional 2-in-1.

That will further depress traditional PC sales, which just contracted for the sixth consecutive quarter, and accelerate sales of tablets. More importantly, it means fewer reasons for business to buy into Microsoft's strategic shift to touch on the desktop, less enthusiasm on the part of corporate application developers to tackle Metro apps, and more motivation for enterprises to experiment with alternative operating systems including Android, Chrome OS, OS X and iOS.

Naturally, Microsoft sees it differently.

Calling Windows 8.1 a "significant milestone" for businesses, Erwin Visser, who heads Windows marketing to corporations, trumpeted the update's emphasis on work. "Windows 8.1 builds on our vision to offer businesses the most powerful and flexible modern operating system across devices, help customers enable their mobile users wherever they are working, and combine that flexibility with the manageability and security IT pros demand," Visser said in a Thursday blog announcing 8.1's availability.

Windows 8 users who had earlier installed the Windows 8.1 developer or release previews that Microsoft offered this year can update to the final version, but after it's completed, must re-install all desktop applications and Metro apps.

Free 90-day evaluation copies of Windows 8.1 Enterprise, the edition usually available only to customers with volume licensing agreements, can be downloaded in disk image (.iso) format from Microsoft's website.

Gregg Keizer covers Microsoft, security issues, Apple, Web browsers and general technology breaking news for Computerworld. Follow Gregg on Twitter at @gkeizer, on Google+ or subscribe to Gregg's RSS feed. His email address is [email protected].

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