(AP) -- Worldwide shipments of personal computers edged back up in the third quarter, according to industry researchers, a promising sign for the industry as it heads into the holiday shopping season.

Last year's holiday quarter was the worst in about six years, and PC shipments declined in the first half of 2009 as the recession inhibited spending by consumers and businesses.

On Wednesday, however, analysts at IDC said from July through September rose 2.3 percent from the same period of last year, as consumers kept buying the low-cost laptops and tiny netbooks that have been the bright spot in the industry.

The Framingham, Mass.-based research group said it had expected shipments to fall nearly 3 percent. A robust back-to-school shopping season and ahead-of-schedule government spending in China and Taiwan helped drive the surprise results.

IDC said such growth just ahead of the Oct. 22 launch of Corp.'s new PC operating system, Windows 7, bodes well for the fourth quarter and next year. The researchers expect to see more businesses replacing aging PCs in the middle of next year.

"Despite the ongoing mix of gloom and caution on the economic front, the PC market continues to rebound quickly," Loren Loverde of IDC said in a statement.

Gartner Inc., another research group, said shipments rose one-half of a percent. Gartner and IDC numbers differ because the groups use slightly different methods for their calculations.

Hewlett-Packard Co. held its spot as the world's biggest . Taiwan's Acer Inc. unseated Inc. at No. 2.

Like HP, Acer is prominent in retail stores, and has done more deals with wireless carriers to subsidize netbooks. Since consumers led the spending in the quarter, HP and Acer benefited while Dell, which is more reliant on corporations, lagged.

But in a statement, Gartner analyst Mikako Kitagawa cautioned that rising shipments and gains in market share aren't predictors of , because the most popular products among consumers are inexpensive, and less profitable for PC makers.

"Revenues and margin performance are key to surviving in a very competitive market," she said.

China-based Lenovo Group Ltd. and Japan's Toshiba Corp. rounded out the top five, according to both IDC and Gartner.

In the U.S., IDC said HP took back the No. 1 spot from Dell, though just barely. Stamford, Conn.-based Gartner said Dell remained at the top in the U.S. by the same margin of half-a-percent of market share.

, Apple Inc. and Toshiba were the third, fourth and fifth-largest PC companies in terms of U.S. shipments, according to both groups.

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