Texas PC builder Dell remained in first place but continued to erode share, dropping from 30.9 percent in the US market to 28 percent. HP was second and jumped from 21.6 to 24.3 percent. Gateway was expected to lose the most and stood to fall by more than 14 percent to claim only 4.8 percent, the report said, though IDC analysts did not say which manufacturers would benefit from Gateway's market slump.

Top 5 US vendors as estimated by IDC

Shifts in world marketshare were distinguished primarily by Acer, the researchers noted. The Taiwan company gained 59.2 percent and jumped to 8.1 percent of all computers shipped based on a doubling of its share in the US and strong results in Europe, the Middle East, and its southeast Asian home. HP extended its lead over Dell and was responsible for 19.6 percent of the entire market compared to the 15.2 percent of Dell, due primarily to better notebook sales.

Apple was excluded from the top five and is known to be below the 4.4 percent of fifth-place Toshiba, though IDC said it did not have specific figures available beyond that number. Global Mac shipments have typically hovered between 2.5 and 3 percent in recent years.

Meanwhile, rival research firm Gartner says Apple's earned an even higher market share for the third quarter, claiming that the Cupertino-based company took 8.1 percent of the US PC market, up from 6.2 percent during the same period one year ago. Apple's market share, according to those numbers, grew 37.2 percent year-over-year, which is more than twice as fast as any other manufacturer ranked in Gartner's top 5 PC vendors. The company, however, was still ranked third in Gartner's top 5 US PC vendor list, behind Dell and HP (respectively).