By Katie Marsal and Kasper Jade

Published: 10:25 PM EST

First on AI: Sales of Apple's Macintosh computers over the past twelve month's have grown faster than any other major PC manufacturer, boosting the company's share of the U.S. PC market to 6.1 percent, according to data released by Gartner on Wednesday.

Between the third calendar quarter of 2005 and the third quarter of 2006, Apple's U.S. Mac unit shipments grew 31 percent from 744,000 units to 975,000 units, preliminary data from the firm shows.

Apple's 6.1 percent share puts it right behind Gateway, whose 6.4 percent share allowed it to maintain its No. 3 position for U.S. PC shipments.

Dell held onto the No. 1 position in the U.S. PC market with a 32.1 percent share despite a 7.1 percent decline in shipments year-over-year. It was followed by HP, which grew its share of the market from 21.2 percent to 23 percent.

Behind Apple in fifth place was Toshiba, which shipped 813,000 units during the third quarter -- good enough for 5.1 percent share.

On the other hand, Apple did not place within the top five PC manufacturers worldwide, and therefore data on its worldwide market share and PC shipments was not included in Gartner's preliminary third quarter results.

"Since these are preliminary figures, we only have the top 5 vendors worldwide at this time and Apple was not in the top 5," a spokesperson for the firm told AppleInsider.

Gartner said Hewlett-Packard regained the No. 1 position for worldwide PC shipments in third quarter for the first time since the fourth quarter of 2003.

HP's 16.3 percent share was followed by Dell with 16.1 percent. Lenovo's 7.5 percent share, Acer's 5.9 percent and Toshiba's 4.3 percent rounded out the top five.

In total, Gartner said worldwide PC shipments totaled 59.1 million units in the third quarter of 2006, a 6.7 percent increase from the same period last year.

At the same time, the U.S. PC market experienced a year-over-year shipment decline of 2 percent. The last time the U.S. PC market suffered a decline in PC shipments was the second quarter of 2002, the firm said.