If Windows 8 is a flop, however, it will increase the pressure on Microsoft CEO Steve Ballmer. His 12-year reign has been marred by the company’s troubles adapting to an Internet-driven upheaval. As Microsoft has stumbled, faster-innovating companies such as Apple and Google have elbowed their way into a position to steer the direction of computing for the next decade or two.

Ballmer, known for his zealous faith in Microsoft, hails Windows 8 as the catalyst for an exciting—and lucrative—new era at the 37-year-old software maker.

Investors seem to be believers, too. Microsoft’s stock gained 52 cents Feb. 28 to close at $31.87, the highest closing price since April 2008. The shares have climbed by 23 percent so far this year. By comparison, Apple’s stock has surged 32 percent during the same period, while Google’s shares have dropped 4 percent.

Microsoft’s financial performance traditionally improves when it releases a new version of Windows. The last upgrade came in October 2009 when Windows 7 hit the market. The company has sold more than 525 million copies of Windows 7 since then. Part of Window 7’s success stemmed from pent-up demand; the previous version, Vista, was so clunky and buggy that many PC users stuck with the system they already had on their machines or switched to Apple’s technology on Mac computers.

Windows 8 is radically different from its predecessors. The system won’t even have Microsoft’s familiar “Start” menu. All applications are spread across a mosaic of tiles, as part of a design Microsoft calls “Metro.” The tiles, which resemble road signs, can be navigated with a swipe of the finger on the display screen or with a keyboard and a computer mouse. The tiles also provide a glimpse at the activity occurring in applications connected to the web, such as eMail.

The system also is expected to enable users to easily back up their pictures, movies, music, and other files on a Microsoft storage service called SkyDrive, which will compete against Apple’s iCloud.

The operating system’s versatility means it can be used to power computer tablets, as well as traditional PCs.

Microsoft badly wants a piece of the tablet market that has been cutting into PC sales since Apple introduced the iPad two years ago.