"All these things will evolve, and the operating system will need to evolve with them," said Ballmer, speaking at a launch event in New York City for the retail version of Microsoft's new operating system, which officially goes on sale in the United States at midnight.

Ballmer, in a dark suit paired with a bold red tie against the backdrop of Manhattan's cavernous Cipriani restaurant, said future operating systems will need to support advanced technologies, such as natural language voice recognition, that are only beginning to show up in mainstream computing. That, said Ballmer, implies that "a platform needs to exist ... that's a very long-lived platform."

Ballmer's remarks run counter to the notion held by some that the move to Web-based applications offered by companies such as Google and eBay will eliminate the need for computer users to run so-called fat operating systems like Windows on their desktops or laptops. Indeed, Microsoft already is at work on a successor to Vista that's code-named Vienna. To date, however, the company has said little about what features it will contain or when it will be released.

Leaving little doubt about the importance the company still places on the operating system, Ballmer on Monday called Windows Vista "the biggest launch in Microsoft's history." He said the vast majority of consumers will experience the operating system by purchasing a new personal computer rather than upgrading old systems. Factory-installed versions of Vista will outpace upgrade sales "by an order of magnitude" in the first 12 months of the release, Ballmer said.

Symbolizing Vista's importance not just to Microsoft but also to PC and chipmakers, Ballmer was flanked at the event by Advanced Micro Devices CEO Hector Ruiz, Toshiba CEO Hisatsugu Nonaka, and Dell CEO Kevin Rollins. Rollins said preorders for Vista-equipped PCs and laptops resulted in a 20% spike in traffic at Dell.com over the weekend, leading to "tens of thousands" of sales.

Also at Ballmer's side under Cipriani's 90-foot, arched ceilings were Intel executive VP Sean Maloney and Hewlett-Packard executive VP Todd Bradley.

To date, more than 5,000 hardware and software products have been certified for use with Windows Vista and more than 2,500 products bearing the Certified for Windows Vista seal will be available when the product officially launches at midnight. According to Microsoft, the operating system also will be available in 19 languages at launch and 99 by year's end.