Microsoft unveils Windows 8

BARCELONA -- You already knew from the early "developer preview" of Windows 8 that Microsoft released in September just how radically different this version of the company's ubiquitous operating system is from its predecessors. But now that Microsoft on Wednesday unleashed a more complete preview version of Windows 8 — which consumers can get their hands on — we really are on the threshold of a whole new era of personal computing.

The stakes for Microsoft and the entire computing ecosystem are enormous. This new era is built around tablets as much as traditional laptops and desktops, and multi-touch as much as the keyboard and mouse. At the same time Microsoft marches toward Windows 8, archrival Apple is revving up a new version of Mac OS X called Mountain Lion.

And Apple has a huge lead in tablets with the iPad, a new version of which is expected to be unveiled in San Francisco next week.

For its part, Windows 8 provides consumers the flexibility to go back and forth between touch and the keyboard and mouse. And this cloud based operating system — Windows 8 is tied into various Microsoft services online, including SkyDrive where you can store and access documents and pictures — is designed to work on all types of hardware.

"With Windows 8, we reimagined the different ways people interact with their PC and how to make everything feel like a natural extension of the device, whether using a Windows 8 tablet, laptop or all-in-one," said Steven Sinofsky, president of the Windows and Windows Live Division at Microsoft. Sinofsky calls Windows 8 "a generational change for Windows."

Microsoft announced the availability of the "consumer preview" at the Mobile World Congress trade show in Barcelona.

This version of Windows 8 isn't quite final but pretty darn close, and you can download it for free at preview.windows.com. I got an early look at it on a Samsung test tablet. (Microsoft says that to date the developer preview received more than 3 million downloads.)

Keep in mind that however far along, this is still a test version that carries some risks. Not all your peripherals or software drivers will be compatible at this stage, and bugs are to be expected. Microsoft says a report will be generated during setup to alert you to known issues. Moreover, the "beta" will eventually expire (and you can't retreat to Windows 7 or earlier versions when that happens), though that's likely to be well after Windows 8 actually goes on sale.

Microsoft wouldn't give firm dates and didn't reveal pricing or other details in Barcelona. But a very reasonable assumption is the fall.

So what can you expect? Highlights:

As with the developer preview, you notice the dramatic turn in Windows from the very start — even before you get to the newly designed Start screen. At your option, you can log in with a picture password, instead of the standard typed password, by "drawing" a chosen image with your finger on the touch-screen in a predetermined pattern. You can see notifications from Twitter and Facebook.

From the Start screen you can view the weather, appointments, contacts, and more — you get to choose how the information is organized.