NEW YORK — Acrobatics, blaring music and plenty of hype accompanied Microsoft Corp.'s long-delayed debut of its new Windows Vista operating system.

Hours before the software went on sale in New York, dancers clad in Microsoft colors dangled from ropes high above street level Monday and unfurled flags to form the red, green, blue and yellow Windows logo against a building wall.

Vista was set to go on sale in 70 countries Tuesday, along with new versions of Microsoft Exchange e-mail software and the flagship Office business suite, which includes Word, Excel and PowerPoint.

Vista's arrival, two years later than promised, comes at a time of change in the world of personal computers.

New Web-based services threaten to challenge Microsoft's dominance in e-mail and word processing. Microsoft faces an even more immediate challenge as it spends a reported $450 million or more this year on marketing. It must convince consumers to buy the new operating system (and a new computer powerful enough to run it) — instead of, say, a high-definition television to watch Sunday's Super Bowl or a new video game system like Sony's PlayStation 3.

There are four consumer versions of Windows Vista, with prices starting at $199 for the Vista Home Basic to $399 for Vista Ultimate, which has enhanced data and security protection. Most older computers are not powerful enough to run Vista but more than adequate for the tasks many people use them for.

"I think people treat (computers) now much more like a television set," said Michael Cherry, an analyst with Directions on Microsoft, an independent researcher that focuses on the company. "If my TV set is starting to go, the people can be green before I admit the color's gone."

That explains Microsoft's emphasis on how the new operating system makes it easier for people to edit and share digital photos, to easily find any document, e-mail message or video through an enhanced search feature, or get real-time weather, news or other information delivered to the desktop through simple programs called "gadgets."

To better understand how people use computers, Microsoft found 50 families from around the world who, over two years, lived with Vista from its early test phase, known as "Beta 1."

Microsoft created a way for these families to send daily feedback — smiles or frowns — and company executives periodically dropped by to observe people using the operating system. This unusual group of beta testers sent 5,000 comments and identified 800 bugs that no one else found.

Trish Miner, research manager for Life with Windows Vista family feedback program, said the program offered surprising insights — like how changes to the Web browsing experience had unintended consequences.

"We had changed the scroll bar, we had kind of made it disappear," Miner said. "You would think we might have caught that ourselves."

There's a simplified feel to the Vista operating system, beginning with the "start" menu that replaces labels like "programs," "documents" and "settings," in favor of self-explanatory terms like "Windows DVD Maker," or "Microsoft Office Word."

Of course, Microsoft couldn't make Vista too different from Windows XP for fear of consumer backlash.

"They can't do anything too radical because if they make too big a change, people will say, 'Oh, I don't want to learn it,' " Cherry said. "Windows is stuck with making incremental improvements that don't annoy the user base too much but still try to find ways to get people who have been resistant to finally purchase their computer."

The Associated Press and the Los Angeles Times contributed to this report.