Worldwide PC shipments rose 15 percent in the quarter, with HP in the lead, followed by Dell Inc.

The July-September period was marked by strong growth in the lower-cost mini-notebook category, which Acer has been focusing on, Gartner analyst Mika Kitagawa said. This helped bolster the overall PC market in he face of slumping consumer spending.

Acer's market share gains in the quarter were driven by surging sales of its mini-notebooks, a segment in which HP and Dell do not have a strong presence, she said.

Mini-notebooks, also known a netbooks, refer to PCs with screen sizes of five to 10 inches. They usually cost less than $500, while standard laptops can cost two to four times as much.

Kitagawa estimated that less than 5 percent of overall PC shipments are mini-notebooks, but she said the market seems to be growing.

Overall, worldwide PC shipments rose 15 percent from last year to 80.6 million units. At the same time, U.S. shipments rose 4.6 percent to 17.4 million units.

HP shipped 14.8 million units in the quarter, for a market share of 18.4 percent, barely changed from a year ago. Dell was in second place with a share of 13.6 percent, down 0.5 percent from last year, while Acer's piece of the market jumped to 12.5 percent from 9.7 percent.

Kitagawa also noted that Acer saw 16 percent U.S. shipment growth from the second quarter, while Dell and HP struggled.

"In general the U.S. market felt the impact of the economic downturn very much, so especially those vendors that are in the professional market, it had much impact," she said.