San Francisco: Microsoft's new Windows 10 operating system debuts tomorrow, as the longtime leader in PC software struggles to carve out a new role in a world where people increasingly rely on smartphones, tablets and information stored online.
No one's expected to line up overnight for Windows 10, the way people did 20 years ago for Windows 95. But Microsoft is counting on tens or even hundreds of millions of people to download its latest release for free in the coming months.
The launch will be accompanied by a global marketing campaign for an event the company hopes will be pivotal - both for its own future and for a vast audience of computer users around the world.
Windows 10 is coming to PCs and tablets first, but it's also designed to run phones, game consoles and even holographic headsets. It has new features, a streamlined Web browser called Edge and a desktop version of Cortana, the online assistant that is Microsoft's answer to Google Now and Apple's Siri.
Still, the company insists Windows 10 will seem familiar to users of Windows 7, the six-year-old operating system still running on most PCs. Microsoft and PC makers want to erase the memory of the last big update, 2012's Windows 8, which alienated many with its jarring, unwieldy design.
Microsoft skipped the name Windows 9, as if to distance itself further from the last release. While many analysts believe Windows 8 made sagging PC sales even worse, it's unclear if Windows 10 will spur the industry back to growth.
Microsoft plans promotional events in several cities tomorrow, tied to a global ad campaign and a series of charitable donations. About 5 million people who enrolled in an earlier test program will be able to download Windows 10 right away.
The company is also offering Windows 10 as a free download, any time over the next year, to anyone who has the Home or Pro versions of Windows 7 or 8 (but not the Enterprise versions used by big organisations).
Some may not get it the first day; Microsoft says it will deliver downloads in waves, to ensure things go smoothly, but it hasn't said how long that will take.
Retailers such as Best Buy, Staples and Wal-Mart will have some desktops and laptops with Windows 10 already installed. More models are coming.
The company wants to get the new software on as many devices as possible. Microsoft needs a large pool of users to convince independent programmers that it's worth their time to build useful or entertaining apps for Windows 10 devices.
CEO Satya Nadella says he wants to have 1 billion devices running Windows 10 in three years. Microsoft estimates there are 1.5 billion people who currently use some kind of Windows.
Rather than charging them to upgrade, as Microsoft used to do, it's embracing the free download model pioneered by Apple and Google.