But don't worry. Your old Windows applications will still run. Like in the earliest versions of Windows that ran DOS software in a special DOS mode, Windows applications will run in a "Desktop" or "Windows 7" mode. Best of all, you'll be able to run old Windows applications side-by-side with the Metro UI app of your choice.
Interestingly, the Metro UI handles files like the iPad -- documents and data files are associated with the application, and will be managed only from within applications. But in the Windows 7 window, you'll still have old-fashioned file management, where your data file locations are not associated with specific applications and can be moved copied, deleted or modified without reference to specific applications.
Note that these two generations of user interface will exist side-by-side only on PCs. Windows 8 will also run on devices powered by ARM chips made by a company called ARM Holdings. Traditionally, these chips power smartphones and tablets, and the slim operating systems designed for these mobile gadgets. Windows 8 will run on ARM devices, but the old interface will not be supported. ARM devices will run only the Metro UI, and the apps written for that platform.
So both your PC and tablet will run Windows 8, but only your PC will be able to run your current version of Office or QuickBooks. On the tablet, you'll have to wait for new, Metro-specific versions to be created.
Why Microsoft is doing this
People resist change. It's just human nature.
Users are going to love the touch-centric computing interfaces of tomorrow. But today, many Windows users just don't like the sound of it.
Whenever I predict desktop tablets, I get a lot of e-mail from the resistance. Touch is too limited, they say. An iPad-like interface is cramped and limiting. The arm position necessary to use a touch screen even at an angle is uncomforable. I need a real keyboard. I've grown attached to my mouse. I need hardcore multi-tasking.
Apple's strategy for overcoming resistance was to launch an entirely new device, rather than immediately replace an existing platform with a new one. Apple's MPG (multitouch, physics and gestures) interface was first used on Apple's first-ever cell phone. Because the entire device category was brand new to Apple, the company didn't ask users of existing Apple products to do things differently. The company's strategy is to start small and move up the food chain - first phones, then tablets, then multi-touch laptop and desktop touchpads, then desktops, which we'll see no doubt this year or next.
What we learned this week is that Microsoft has come up with an entirely different solution to the problem of user resistance to change: Microsoft intends to get us all using a touch interface with mice and keyboards first.
By the time we get used to doing that, we'll be happy to get rid of the peripheral hardware and just use our desktops like iPads, touching the screen directly. It will be the same interface, but much better because we'll be able to use multi-finger gestures and because we'll enjoy the innate psychological payoff of using an MPG device.
I think Microsoft's strategy is brilliant. I had all but written off Microsoft as clueless about the future of touch computing. But the company's latest demo changes everything.
Mike Elgan writes about technology and tech culture. Contact and learn more about Mike at Elgan.com, or subscribe to his free e-mail newsletter, Mike's List.