There’s a smug maxim in Silicon Valley and the places that imitate it: “To survive, you must destroy your company every x years” (where x varies according to how much the speaker wants to stress the pace of technological change). Sometimes attributed to Intel’s former chief executive Andy Grove, it is a maxim more repeated than observed. But it can be a lovely and startling thing when a large, publicly traded company takes a big bet by replacing its core product.

Microsoft’s new Windows 8 operating system, which went on sale last Friday, is the most dramatic gamble by a technology company since Intel abandoned the memory market to make semiconductors in the 1980s. Windows is a civilizational tool; there are more than a billion Windows users around the planet. But when, after being given a new personal computer by their IT manager or buying a new device for themselves, those users boot up the new OS, they’ll recognize nothing.

Gone is the familiar “Start” button and user interface that Microsoft has employed since it launched Windows 95, 17 years ago. In its place, users will find a screen of shifting colorful tiles. If they’ve set up a Microsoft account with Outlook, their e-mail, calendar, and contacts will appear automatically; if their account is linked to Facebook, the faces of their Facebook friends will begin blinking in a People tile, and the photos they’ve posted to Facebook will float into a Live tile. To its new users, Windows 8 will seem as personal—and as noncorporate—as their smartphones or tablet computers, and that’s the whole idea.

Windows 8 can be used on a conventional personal computer with a mouse or touchpad, but doing so is weird and confusing. The operating system works best with a touch screen, where users can swipe and touch tiles and icons. (The nearest thing in Windows 8 to the old Start button, the Charms panel, can be reached most conveniently with a rightward swipe.) Remarkably, in order to show off the new functionality of Windows 8, Microsoft is selling its first computer: the Surface, a $499 touch-screen tablet whose cover is a small keyboard, allowing the device to function as a small laptop.

Windows 8 and Surface are beautiful, elegant, and innovative, which are not qualities one associates with Microsoft’s products. They are mostly the work of the president of the company’s Windows division, Steven Sinofsky, a computer scientist, yoga practitioner, and devotee of management theory, who keeps a much-read blog at MSDN, the Microsoft developer network. There, in a long post on the history of interfaces and the thinking behind Windows 8, he wrote, “The new Windows 8 user experience is no less than a bet on the future of computing, and stakes a claim to Windows’ role in that future.” He defended the radical nature of the design and deflated worries that Windows users would never accept the new interface.

Last week, the crush at Microsoft’s new Times Square store in New York reminded observers of the crowds at the launch of a much-anticipated Apple product ―which must have been the company’s hope. (Although there was unkind talk suggesting that the crowds had been bought with hundred dollar coupons and the spectacle of beat boxers.) But to a very large degree, Sinofsky’s bet has the logic of desperation. Seventeen years ago, there were no competitors to Microsoft’s foundational business: developing and selling what the computer industry calls “platforms,” the software upon which other developers’ software must run and with which hardware must work. Today, the Web is the platform for most computing, and Apple’s iOS (the operating system of the iPhone and iPad) and Google’s Android are the platforms for mobile devices. The sharp edges between business and consumer computing have melted. Microsoft had no choice but to try something new.

It’s an interesting historical moment for the two founding companies of the personal-computing revolution. Microsoft knows it’s slowly dying, and declines to accept its fate; Apple, flush with cash, doesn’t yet have to admit that with the death of its tutelary genius, it has lost its way. But secretly, its executives, designers, and developers must fear that something is badly wrong. Steve always said that technology companies began to die when salespeople and bean counters started making the decisions about products. The announcement on October 29th that Scott Forstall, who ran software development for the company’s iPhone and iPad products, had been fired along with the Apple’s retail chief, John Browett, only confirmed the sense of a company that had lost its direction without its leader.

Forstall’s division was responsible for shipping the grossly buggy mobile maps service with the most recent upgrade to iOS. The outcry from iPhone users, unused to such bad software from the company they loved most, embarrassed Apple’s executives, but Forestall declined to sign an apology, forcing Cook to write the apology himself. Relations between Forstall and Jony Ive, the company’s chief designer, had declined to such a state, according to numerous accounts in the press, that the two could no longer share a room. While Jobs was still alive, he could adjudicate disagreements among his senior managers, as Chairman Mao had forced consensus from a divided politburo of powerful chieftains; but, without its founder, Apple has lost its unifying vision.

This story originally appeared in the Financial Times.