Microsoft says it has sold 240 million Windows 7 licenses since releasing the operating system to retailers a year ago, making it the fastest-selling OS in the company's history.

Also, as of September, the successor to the much-maligned Windows Vista was running on 93% of new consumer PCs, Microsoft said Thursday. According to Web metrics firm Net Applications, Windows 7 accounted for 17.1% of the global OS market as of the end of September and had surpassed Vista in July.

In the six months after Windows 7 started appearing on store shelves, all of Microsoft's more than 18,000 computer-making partners were selling PCs with the new OS. That compared with 70% during the same period for Vista.

In general, Microsoft software has been getting higher marks from consumers. In 2007, the first full year Vista was available, the company's rating on the American Customer Satisfaction Index was a 70, which is less than the 75 rating for all other software makers. This year's, Microsoft's rating is 76, while other software makers as a group scored 77. (The ACSI scores on a 0-100 scale.)

Microsoft's bottom line has benefited from the success of Windows 7. In the fourth fiscal quarter ended June 30, Windows and Office, the company's two workhorses, drove a 48% increase in profit year over year and a 22% jump in revenue.

At the time, the company benefited from businesses increasing spending to replace older computers that companies had held onto during last year's recession. Microsoft's Windows and Windows Live Division reported a 44% jump in revenue year to year, to $4.6 billion, driven mostly by Windows 7 sales.

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