Notebook PC shipments rose almost 40 percent in the quarter compared to the same period in 2007 to hit 38.6 million units. Desktop PC shipments declined by 1.3 percent for the same period to 38.5 million units.

The crossover point had been widely predicted by Intel Corp. and others for some time. Declines in the price of flat-panel displays and a rise in the availability of mobile networks such as Wi-Fi have fueled notebook sales among business and consumer users.

"The notebook PC is no longer a tool only for the business market, or a computer for the well-off consumer; it's now a computer for everyone," said Matthew Wilkins, principal analyst for compute platforms at iSuppli.

The quarter was a strong one overall for PCs, despite the global downturn. Worldwide PC unit shipments rose to 79 million units, 15.4 percent over the third quarter of 2007.

Sales exceeded iSuppli's expectations of 12 percent year-over-year growth, for4cing the market watcher to nudge its full year 2008 unit growth forecast from 12.5 to 13 percent. The company did not change its forecast for 4.3 percent PC sales growth in 2009, slashed in November from its original projection of 11.9 percent.

In November Intel warned its fourth quarter revenues could fall by as much as $2.2 billion. Wall Street analysts have cut 2008 projections for both Intel and archrival Advanced Micro Devices.

"While the third quarter will be remembered as the time when the scale of the global economic/credit crunch truly became apparent, the PC market managed to deliver strong unit shipment growth during the period," Wilkins said.

The rankings of the top five PC makers were unchanged for the quarter. Hewlett-Packard remained the largest supplier with shipments of 14.9 million units, and a market share of 18.8 percent.

Dell Inc. was second with shipments of slightly less than 11 million units and a 13.9 percent market share. Hard on Dell's heels, Taiwan's Acer Inc. shipped 9.7 million systems giving it a 12.2 percent market share, less than two points away from the number two spot. Lenovo and Toshiba Corp., ranked fourth and fifth, with market shares of 7.5 and 4.6 percent, respectively.

"The big news from iSuppli's market share data for the third quarter was undoubtedly the performance of Acer," Wilkins said. "On a sequential basis, the company grew its unit shipment market share by 45 percent, and by 79 percent on a year-over-year basis."

Netbooks--ultra small subnotebook designs popularized by the Asus eePC--were a strong suit for Acer. The company shipped nearly three million more notebooks in the third quarter than in previous quarter, the majority of them netbook products.

Intel reported in October it had sold as much as $200 million in Atom processors and chip sets, mainly for netbooks.

For its part, Apple Inc. lost almost half a point of market share on a sequential basis at 3.2 percent, placing it seventh overall in total PC shipments. AsusTek Computer Inc. reported strong performance with its notebook shipments, surpassing Lenovo to become the fifth-largest notebook PC OEM while retaining its position overall as the sixth-ranked PC OEM in terms of total PC shipments.