Schmidt maintains Microsoft sometimes unfairly rigs its operating system to limit consumer choices — something that Microsoft has consistently denied doing. Google fears Microsoft could limit access to its search engine and other products if Windows is set up to favor Microsoft products in the default settings.

Page and Brin have frequently derided Windows as a clunky operating system susceptible to computer viruses and other security problems.

Google made a veiled reference to Windows' perceived shortcomings in its blog posting.

"We hear a lot from our users and their message is clear — computers need to get better," wrote Sundar Pichai, Google's vice president of product management and Linus Upson, Google's engineering director.

A Microsoft spokesman didn't immediately respond to an e-mail request for comment sent early Wednesday morning.

Schmidt and Brin are expected to discuss Google's new operating system later this week when they appear at a media conference hosted by Allen & Co. at the Sun Valley resort in Idaho.

Despite its own power and prominence, Google won't have an easy time changing the status quo that has governed the personal computing industry for so long.

As an example of how difficult it is to topple a long-established market leader, Google estimates about 30 million people are now using its Chrome browser — a fraction of those that rely on Microsoft's market-leading Internet Explorer. And there have been various attempts to develop open-source software to undermine Microsoft with relatively little effect.

The Chrome operating system will run in a new windowing system on top of a Linux kernel — computer coding that has been the foundation for the open-source software movement for nearly two decades.

Google has already introduced an operating system for mobile devices, called Android, that vies against various other systems, including ones made by Microsoft and Apple Inc.

The Android system worked well enough to entice some computer makers to begin developing netbooks that will eventually run on it.

Google, though, apparently believes a Chrome-based system will be better suited for running applications in netbooks.

"We believe choice will drive innovation for the benefit of everyone, including Google," wrote Pichai and Upson.