Shipments of PCs worldwide were better than expected in the third quarter of 2009, thanks to strong sales of low-cost netbooks. But the big surprise was that up-and-comer Acer, bolstered by its netbook lineup, surpassed Dell to become the second largest PC maker in the world. HP retained the number one spot.

Analysts at both Gartner and IDC had expected PC sales to dip a bit when compared to the same quarter one year ago. But PC sales actually rose in the quarter, by about 1.4 percent. Of course, since the gains are being made largely by netbooks and other very low cost PCs, revenues are down: The average selling price of a PC in Q3 2009 was 20 percent lower than a year before.

HP dominates the worldwide PC market with about 20 percent of the market. New number two Acer accounted for 14.7 percent, while Dell, slipping to third place, commanded 11.4 percent. Rounding out the top five are Lenovo and Toshiba. (Sorry, Mac fans: Apple continues to command less than 4 percent market share worldwide and does not factor into the list of top PC makers outside of the United States.)

Acer's sudden surge came courtesy of a 26 percent gain in the quarter, by far the fastest growth among all PC makers. The company markets popular netbooks such as the Aspire One, and recently launched a Timeline notebook that achieves over 8 hours of battery life. Dell, meanwhile, does market a netbook line to consumers but still primarily serves businesses—80 percent of Dell's sales are to businesses.

In the United States, meanwhile, the market share figures for Q3 2009 are quite different. Here, Dell is the number one PC maker with 26.2 percent market share, followed closely by HP (25.7 percent). Rounding out the top five are Acer (13.0 percent), Apple (8.8 percent), and Toshiba (8 percent).

Looking ahead, Windows 7 launches in just a week, and analysts expect a healthy year-over-year bump in PC sales, perhaps as much as 30 percent. But much of that disparity is due to unusually low PC sales, due to ongoing economic conditions