Microsoft launched a radical redesign of its world-dominating Windows operating system Thursday, introducing a touch-enabled interface that attempts to bridge the gap between personal computers and fast-growing mobile devices powered by the company's fiercest competitors.
The debut of Windows 8 heralded the biggest change to the system since 1995, when the company first offered built-in Internet support. And with so much riding on it, the overhaul could be Microsoft's most important product since co-founder Bill Gates won the contract to build an operating system for IBM Corp.'s first PC in 1981.
To succeed, the new version will have to be innovative and elegant enough to attract consumers who've fallen in love with notebook computers, tablets and smartphones running software from Apple and Google.
"What you have seen and heard should leave no doubt that Windows 8 will shatter the perceptions about what a PC really is," Microsoft CEO Steve Ballmer crowed at a New York event to kick off the Windows promotional campaign.
The first PCs and other devices running Windows 8 were to go on sale Friday.
The software is designed for use on a variety of machines — desktop PCs, notebook computers and tablets, including Microsoft's new Surface tablet, the first computing device the company has manufactured after focusing almost exclusively on software for more than 30 years.
The redesigned operating system represents an attempt to pull off a difficult balancing act as Microsoft maintains its highly profitable heritage in software while trying to get a foothold in the newer, more fertile field of mobile devices.
So far, the booming mobile device market has been defined by Apple's trend-setting iPhone and iPad, Google's pervasive Android software and Amazon's Kindle Fire tablets. Tablets have been undercutting the sales of desktop and laptop computers since Apple released its pioneering iPad in 2010.
Another version of Windows 8 will be released next week for smartphones, which are overwhelmingly dominated by Apple Inc. and Google Inc.'s Android software.
Microsoft is also opening a Windows 8 store featuring applications built to run on the system. The store is similar to the apps stores of Apple and Google and will include many of the same services.
More than a billion PCs currently run on Windows, including 670 million that use Windows 7, the last version of the operating system, released in 2009.
But the owners of most existing Windows machines aren't expected to switch to Windows 8 for at least a year, maybe longer. That means most of Windows 8's early usage will come from consumers, businesses and government agencies that buy new devices with Windows 8 already installed.
There were few surprises at Thursday's launch event because Microsoft Corp. has been previewing preliminary versions of Windows 8 for the past 13 months — part of 1 billion hours of testing.
Still, the overhaul poses a big risk for the Redmond, Wash., company because Windows 8 looks and operates so much differently than previous versions.
"This is the biggest gamble they've ever made," said analyst Richard Doherty of the Envisioneering Group. "Does (Windows 8) do more things? Yes ... but it's not that easy to use."
Even when users revert to a desktop mode, the redesign discards the familiar "start" button and menu that Windows has had for 17 years, a change that critics believe will almost certainly provoke howls of protest. But many reviewers applaud Microsoft for greeting users with a mosaic of tiles displaying applications instead of relying on the desktop icons that served as the welcome mat for years.