Apple Inc.'s share of the U.S. personal computer market for the third calendar quarter of 2007 was 8.1 percent, up from 6.2 percent during the same period one year ago, according to preliminary results released from Gartner on Wednesday.

The Cupertino-based company's U.S. Mac shipments grew 37.2 percent year-over-year — more than twice as fast as any other manufacturer ranked in Gartner's top 5 PC vendors for the three-month period ending September — helping it snag a spot as the No. 3 U.S. PC vendor overall.

Apple's US-based Mac shipments during the quarter totaled 1,338,000, compared just 975,000 during the same time last year. Hewlett-Packard and Toshiba also posted somewhat healthy growth during the quarter of 16.5 percent and 16.3 percent to garner a 25.7 percent 5.7 percent share of the U.S. market, respectively.

Growth in notebook sales continued to lead the overall U.S. market, Gartner said, with notebook volume exceeding desktops for the first time ever in the third quarter of 2007. However, both the home and professional markets registered weaker than expected growth.

"Economic uncertainty around the sub-prime mortgage lending and lower consumer confidence may have played a role in challenges vendors faced in the U.S. market," said Mikako Kitagawa, principal analyst for Gartnerâs Client Computing Markets group. "The third quarter is typically a consumer quarter, driven by back to school sales. However, the preliminary results show that back to school sales were softer than expected in the U.S. market."

Dell was able to maintain the No. 1 position in the U.S. market although its year-over-year growth rate was well below the U.S. average, declining 5.5 percent. The decline was mainly attributed to weaker consumer growth.

Apple did not rank in Gartner's top 5 worldwide PC vendors, No. 5 of which was Toshiba with a 4.4 percent share.