Oct. 21--Windows Vista may have driven Sandra Lew straight into Apple's arms. There's a chance Windows 7 could win her back.

"My last laptop had Vista, and it was a terrible experience," said Lew, a 28-year-old marketing specialist who was shopping for a new computer at a Fry's electronics store in San Jose last week.

Though recently unemployed, and watching her wallet, Lew said her frustration with Microsoft's widely criticized Vista operating system was making her lean toward a more expensive MacBook that runs Apple's software instead. But she had heard good things about Microsoft's new Windows 7, and she planned to do more research before making a final choice.

Microsoft is counting on its new operating system, which goes on sale today, to mend relations with customers like Lew and to shore up what is a core business for the world's largest software company. And the $244 billion-a-year PC industry is fervently hoping the new software will help bring buyers back into stores, after a steep drop in sales earlier this year.

Windows 7 has received favorable reviews thus far. But rather than create an immediate sales bonanza, experts caution that it is more likely to have an impact over the long term.

Microsoft still dominates the PC operating system, with Windows Vista or its predecessor Windows XP running on 88 percent of PCs in the United States and 90 percent worldwide, according to the Gartner research firm. But even if that's unlikely

to change in the near term, there are signs that Windows' ubiquity is waning a bit.

Since its release two years ago as the intended successor to XP, Vista has been widely panned as bloated and slow. In the United States, Apple has increased its market share for computers running the Mac operating system. And some PC makers have even toyed with the idea of using Linux or Google's Android for low-powered netbooks.

Meanwhile, PC makers have been clobbered by a recession that slowed new computer sales early in 2009, for the first time in years. Some analysts have suggested that Windows 7 could be a powerful force, along with the recovering economy and upcoming holiday sales, for stimulating new purchases in the second half of 2009.

"The launch of Windows 7 will be a major positive for the PC industry," predicted analyst Matthew Wilkins at iSuppli, an industry research firm.

Retailers like Best Buy are planning promotions around the new release.