SAN FRANCISCO -- Apple's ( AAPL) Mac operating system continues to win over a growing number of computer users and chip away at the dominant lead of Microsoft ( MSFT) Windows. Data tracker Net Applications said Monday that Apple's global share of the personal computer market rose to 6.6% in September, up from 4.7% in the same month last year, and higher than 6.15% in August. Net Applications attributes the gains to Apple's use of faster Intel ( INTC) processors in its Mac. Intel-based Macs began shipping in January 2006. The increase in market share showcases Apple's growing appeal to consumers outside its traditional niche audience of Mac enthusiasts, graphic artists and educational professionals. In addition to the use of Intel processors, analysts and investors say the company's wildly popular iPod has brought more attention to its computers -- the so-called halo effect -- helping it capture a greater share of the mainstream market. Microsoft's Windows operating system still commands the vast majority of the computer market. But its total market share fell to 91% in September from 94% a year earlier. Vista, the latest version of Windows, held about 7.4% of the market in September. Investors expect Apple to notch further market share gains after it releases its Leopard operating system in October. The company demonstrated a preliminary version of Leopard in June, highlighting features to help users organize email and desktop applications and run Microsoft applications.