REDMOND, Wash. (AP) -- Microsoft Corp. is expected to report another quarter of lackluster growth as the software maker prepares to release a much-anticipated overhaul of its Windows operating system.

The company's fiscal third-quarter results, due out after the stock market closes Thursday, will likely show Microsoft has been having trouble selling more copies of Windows' older versions with the release of the new product on the horizon.

Microsoft hasn't announced when the revamped operating system, Windows 8, will hit the market. Most analysts predict the software will go on sale in September or October.

Windows 8 is being counted on to spur more sales of personal computer while also giving Microsoft a chance to compete against Apple Inc.'s popular iPad in the tablet computer market.

The new operating system can serve a dual purpose because Microsoft designed it to run on devices that can be controlled by touch, as well as keyboards and computer mice.

The high hopes riding on Windows 8 are the main reason Microsoft's stock price has risen by about 20 percent so far this year, eclipsing a 16 percent gain in the technology-driven Nasdaq composite index. Microsoft shares closed Wednesday at $31.14.

But the buildup to Windows 8 has a downside, too, by giving consumers and businesses another reason to buy some of the desktop and laptop computers already on the market. The reduced demand has contributed to revenue declines in Microsoft's Windows division, its most profitable line of business. Windows revenue has declined from the previous year in four of the previous five quarters.

The success of the iPad, which runs on Apple's mobile operating system, also has siphoned away PC sales.

Microsoft's most robust growth recent quarters has come within its entertainment division that makes its Xbox 360 video game console and Kinect motion controller. The company, which is based in Redmond, Wash., also has been paring its losses within its online division, which has struggled for years to compete against Internet search leader Google Inc.

Analysts, on average, are expecting Microsoft's total revenue for the January-to-March period to increase by about 4 percent from last year to nearly $17.2 billion, according to FactSet. The analyst forecast calls for earnings per share of 58 cents, down from 61 cents at the same time last year.