Microsoft kicks off Windows 8

• Dramatic overhaul of Windows goes on sale Friday
• Lenovo, Sony, Toshiba, Dell and HP are showing off new Windows 8 machines
• Windows 8 works on both tablets and PCs

NEW YORK — Can Microsoft capture the imaginations of tech consumers again, as rival Apple has?

That was the subtext Thursday for a splashy launch for Windows 8, the new operating system upgrade that Microsoft begins selling Friday at 12:01 a.m.

"What you've seen and heard should leave no doubt that Windows 8 shatters perceptions of what a PC truly is," said Microsoft CEO Steve Ballmer. "We've reimagined Windows, and kicked off a new era for Microsoft and our customers."

For the first time, the new Windows has a touchscreen interface, with moveable tiles. For older computers that upgrade, the touchscreen will not be accessible, but the tiles can be accessed by mouse or touch pad.

Microsoft says that 1 billion people use Windows, with 670 million on Windows 7, which was introduced in 2009.

At the launch, PC partners including Lenovo, Sony, Toshiba, Dell and Hewlett-Packard showed off new Windows computers. Many of the laptops have splashy new designs with removable screens that morph into portable tablets.

Microsoft's operating system works on tablets and traditional PCs and laptops. Despite twin versions, Windows 8 and Windows RT, Microsoft is taking a notably different, and perhaps riskier, course than rival Apple. Apple still markets separate operating systems for Macintosh computers (OS X Mountain Lion) and for the iPhone, iPad and iPod Touch (iOS 6), even though some features are common to both operating systems.

Gartner analyst Michael Gartenberg says Microsoft is off to a good start.

"I think they did a really good job of reintroducing themselves to the consumer today, Microsoft, not just Windows. This was about Windows and Windows RT and SkyDrive and Skype. It was an ecosystem story."

He says part of Microsoft's challenge is to explain to consumers why the radically different approach is better,

"Consumers have shown a willingness to learn. They learned how to use mice and keyboards, they learned how to use touch and pinch-to-zoom. They can learn how to do this too," he says.

Microsoft's unified approach to the operating system is based on its belief that touchscreens will soon dominate PCs, says Ross Rubin, principal analyst at Reticle Research.

"Rather than come to market with another tablet operating system—seeing how (Google's) Android has struggled in that space— they (Microsoft) decided to leverage the high shipping volumes of PCs every year in order to build developer support for a tablet operating system," he says.