makes dramatic changes to an operating system that has been powering PCs for decades.
Internet Explorer 10 initially is being introduced Tuesday to Windows 7 users in a "preview," or test, mode. The new browser isn't compatible with XP, Vista and any other older Windows version.
Although Microsoft is staking its future on Windows 8, far more PCs rely on Windows 7. Microsoft Corp. says more than 670 million licenses for Windows 7 have been sold since its release in 2009. Windows 8 is unlikely to approach that level of usage until at least 2014, based on analyst forecasts.
Desktops, laptops and tablet computers running on Windows 8 are sold with Internet Explorer 10 already installed. Those with older Windows versions will have to download and install the new browser separately.
Although Internet Explorer 10 is supposed to process Web pages more quickly and smoothly than its predecessors, it may have limited appeal to Windows 7 users.
That's because Microsoft primarily designed Internet Explorer 10 for tablet computers and other devices, including a new breed of PCs that have touch-screen displays. Relatively few Windows 7 PCs can be controlled with fingers on a display screen.
Microsoft is hoping many website developers will download and install Internet Explorer 10 on their Windows 7 machines and see the browser's potential for making online services more compelling and dynamic. If that happens, more websites may include features that take advantage of Internet Explorer 10's full capabilities on the bevy of Windows 8 machines expected to be sold during the next year, said Ryan Gavin, Microsoft's general manager for the browser.
Internet Explorer 10's main purpose is to make viewing websites as enjoyable and convenient as using applications tailor-made for specific mobile devices.
For instance, when reading an article on a news site, users of Internet Explorer 10 can just swipe across the screen to continue reading the next page instead of having to scroll down to click on a link, as most browsers require. Microsoft also says games such as "Contre Jour" played on Internet Explorer 10 will work as well, or even better, than those packaged in applications.
Realizing that goal is crucial to Microsoft as it tries to make a bigger splash in the smartphone and tablet markets. It probably will take years before mobile devices running on Windows 8 boast as many applications as their competitors, giving Microsoft an added incentive to build a superior Web browser. The mobile operating systems designed by Apple Inc. and Google Inc. each boast more than 700,000 applications.
Microsoft also hopes Internet Explorer 10 can reverse recent trends in the Web browser market. By some estimates, Google's Chrome browser has supplanted Internet Explorer as the world's most popular browser. Other research firms still assert that Internet Explorer remains the most widely used, although all measures show it has been losing market share to Chrome, Mozilla's Firefox and Apple's Safari.