Microsoft Corp launched Windows 7 on Thursday in its most important release for more than a decade, aiming to win back customers after the disappointing Vista and strengthen its grip on the PC market.

The world's largest software company, which powers more than 90 per cent of personal computers, has received good reviews for the new operating system, which it hopes will grab back the impetus in new technology from rivals Apple Inc and Google Inc.

"It's the first really significant release of Windows in a decade," analyst Brendan Barnicle of Pacific Crest Securities said Television. "Given the missteps around Vista, people really questioned Microsoft's relevancy in the technology space. So this is a critical first step for Microsoft regaining that credibility."

The new system -- which is faster, less cluttered and has new touch-screen features -- comes almost three years after the launch of Vista, whose complexity frustrated many home users and turned off business customers.

The success of Windows -- which accounts for more than half of Microsoft's profit -- is crucial for Chief Executive Steve Ballmer to revive the company's image as the world's most important software firm.

"I have to say I'm chomping at the bit," Ballmer told an audience of Microsoft customers and partners in Toronto on Wednesday, adding that he is ready to make sales calls himself on Windows 7.

Sales won't immediately impact the bottom line of Microsoft, which is expected to post a lower quarterly profit on Friday.

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