Hewlett-Packard Co.’s (NYSE: HPQ) six-year reign as the world’s top personal-computer maker was ended by China’s Lenovo Group Ltd., highlighting the challenges facing Chief Executive Officer Meg Whitman as she strives to revive growth at the 73-year-old technology U.S. company.

Lenovo, which made a deeper push into the market by acquiring International Business Machines Corp.’s PC unit seven years ago, accounted for 15.7 percent of global shipments in the third quarter, compared to 15.5 percent for Hewlett-Packard, according to market-research firm Gartner Inc.

Hewlett-Packard, which has held the top spot since 2006, lost share amid management upheaval and strategy shifts that included the possible spin-off of the PC division, a prospect Whitman later abandoned. The company has been harder hit by an industrywide slump caused by economic malaise and a shift away from traditional computers toward mobile devices, such as Apple Inc.’s iPad.

“In addition to acquiring other vendors, Lenovo has also taken an aggressive position on pricing, especially in the professional market,” the researcher wrote in a statement. “As a result, Lenovo has achieved significant market-share gains over the last two years, exceeding regional average growth rates across all regions.”

Beijing-based Lenovo has been building up the PC franchise it acquired from IBM.

Hewlett-Packard’s PC sales slumped after the company said it would consider spinning off the division last summer, a decision Whitman reversed soon after taking the top job. She told analysts on the last earnings call that the company would “defend our No. 1 position” in PCs.

Intel Affected

The PC-growth slowdown is also hampering technology industry bellwethers Intel Corp. and Microsoft Corp. Intel is on pace to report its first sequential third-quarter sales drop in more than two decades, while analysts have predicted that Microsoft this quarter will suffer its first sales decline in two years.

The PC data released today contrasts with the previous decade when the PC industry experienced double-digit growth most years ascompanies and households bought up notebook computers. Those purchases have slumped as more people spend on Apple’s iPad or new smartphones.

The PC industry is seeking a boost from the introduction this month of the new version of Microsoft’s flagship operating system.