Microsoft's much-heralded Windows 7 operating system made its global debut on Thursday.

By the time the day was a minute old, Microsoft workers were handing out Windows 7 software as gifts at a party the US technology giant held at a San Francisco night club to coincide with a Web 2.0 Summit here.

"Now is the start; now we see if real people love Windows," Microsoft general manager of Windows Live business group said on the eve of the launch.

Feedback from millions of test users of Windows 7 has Microsoft confident they have hit the mark with the new-generation operating system, which reportedly logged more pre-orders in Britain than did the final Harry Potter book.

"This is the most customer excitement we've had in a long time for a Windows release," Hall said.

Microsoft is also celebrating the availability of Windows 7 with parties and by opening its first retail shop in the US city of Scottsdale, Arizona.

The shop features laptops, netbooks, personal computers, Zune players, Xbox 360 videogame consoles, and mobile phones running on Microsoft software.

A second Microsoft store will open in Northern California next week.

"Our customers have told us they want choice, better value and great service when shopping for technology, and that is what we will deliver through our Microsoft stores," said Microsoft corporate vice president of retail David Porter.

Microsoft hired Porter, a retail industry veteran, in February to open retail stores that challenge the successful chain of Apple Stores operated by the maker of iPhones, iPods, and Macintosh computers.

The launch of Windows 7 is expected to open the flood gates for low-priced, feature-rich personal computers based on the operating system.

"We have great PCs (personal computers) coming out for Windows 7," Hall said.

"For most people, Windows is a thing that runs their PC. So when they get a great PC at a great price that works with the other devices they have, that's a win for Windows."

Microsoft releases Windows 7 to the world as it tries to regain its stride after an embarrassing stumble with the previous generation operating system Vista.

"It's a big deal for Microsoft," analyst Rob Enderle of Enderle Group in Silicon Valley said of the Windows 7 launch. "Windows Vista was a train wreck."

While computer users may not give much thought to operating systems that serve as the brains of their machines, the programs are at the heart of Microsoft's global software empire.

Microsoft operating systems run more than 90 percent of the computers on Earth.

Microsoft apparently learned a lesson from Vista and worked closely with computer makers, users and software developers while crafting Windows 7.

More than eight million people have dabbled with Windows 7 since Microsoft began a beta test phase in January, according to Parri Munsell, director of consumer product management for the Windows client group.

Early reviews praise Windows 7 for being everything Vista should have been.