Worldwide shipments of personal computers rose more than 17 percent in the third quarter as consumers flocked to lower-cost and portable PCs, two technology research firms reported Monday.

Dell Inc. (search) maintained its position as the world's leading PC maker, posting growth that roughly matched the industrywide gains reported by Framingham, Mass.-based IDC (search) and Stamford, Conn.-based Gartner Inc. (search)

Worldwide shipments grew 17.1 percent in the July-September period to 52.8 million, according to preliminary data from IDC. That compared with 13.5 percent growth in the same quarter a year ago and an 18.2 percent increase in this year's second quarter.

Gartner, which uses slightly different methods to measure the activity, put third-quarter growth at 17.2 percent, and shipments at roughly 55 million.

The growth remained stronger in overseas markets than in the United States, where IDC put the increase at 11 percent and Gartner at 10.5 percent.

Both firms cited strong demand for portable PCs and an increasingly broad range of low-cost laptop and desktop models.

"These factors sped up new PC adoption and replacement activities," said Charles Smulders, a Gartner vice president. "Overall market growth exceeded expectations, with home demand for mobile being particularly strong."

IDC, which in August predicted third-quarter growth of 13.3 percent, said the gains came despite climbing interest rates and oil prices that have clouded the economic outlook.

"Currently, the economic environment is not the critical factor affecting PC adoption cycles," said Loren Loverde, director of IDC's Worldwide Quarterly PC Tracker. "What we're seeing now is a combination of PC replacements and new users responding to low-price milestones."

However, Loverde said he expects the rate of growth to begin slowing early next year.

IDC said Dell and No. 2 PC maker Hewlett-Packard Co. posted roughly equal growth in PC shipments: 17.8 percent for Round Rock, Texas-based Dell, and 17.9 percent for Palo Alto, Calif.-based H-P.

But Gartner reported an even wider margin between the two, with 18.5 percent growth for H-P and 17.6 percent for Dell.

Taiwan-based Acer posted the strongest growth among top vendors, with 54 percent growth in the quarter.

IDC put Dell's market share at 18.0 percent, up from 17.9 percent a year ago. H-P's market share rose to 16.0 percent from 15.9 percent.

Lenovo, which acquired IBM's PC business during the second quarter, ranked third with a post-merger 7.7 percent market share, followed by No. 4 Acer Inc. at 4.7 percent and No. 5 Fujitsu/Siemens at 3.8 percent.