Microsoft is putting the Windows client OS on a diet as a way to bring the PC OS into the age of cloud computing.

Windows 7, Vista's follow-up, already will be a thinner, more streamlined OS, replacing some of the software Microsoft previously included with the OS with Web-based Windows Live Services. And if comments made by Chief Software Architect Ray Ozzie at Microsoft's Professional Developers Conference (PDC) this week are any indication, Windows will slim down even further in the future, returning to the original intent of an OS -- a way to optimize the hardware it runs on -- instead of being a bloated piece of software whose performance and value rely on compatibility with installed applications.

"The purpose of the OS on the device is to have the best value on that device," Ozzie said at PDC in an interview with the IDG News Service, adding that there is still "tremendous opportunity for innovation" for using the OS to leverage device hardware.

He said that in the future Windows will have "base connections to the Internet" so people can connect to the Web through a browser and services like Windows Update.

But Microsoft won't rely too heavily on the Internet to achieve its goal to support innovative hardware features -- such as touchscreen capability -- so people in places without reliable connections to the Web can still reap the benefits of the OS, he said.

This slimming down of the client OS is as much a way for Microsoft to keep Windows relevant as a hardware OS as it is for the company to concede to the new cloud-computing and services paradigm that Google, Amazon and other companies are pioneering.

Vista might have been a good place to start this evolution, but Microsoft missed the opportunity, said Brian Madden, an independent technology analyst in San Francisco.

He said Vista "would have been great" if it had come out in the late 1990s or even in the early part of the 21st century, the height of the trend to use client-side applications on PCs that is rapidly becoming obsolete as hosted services evolve.

"Vista to me is the culmination of the old way of thinking as the desktop should be," he said, and the fact that it came out in 2007, as the industry was shifting from packaged software to Web-based applications, was "a huge disaster."

Madden called the company's plan to evolve Windows to be lighter and nimble a "reluctant" one. "Microsoft is not leading the way down this path, they're being dragged kicking and screaming by companies like Google," he said.

Andrew Brust, chief, new technology at consulting firm TwentysixNew York, a Microsoft technology partner, has a different take on Microsoft's planned evolution for Windows. He said that the company is trying to re-emphasize the value of having a strong client powered by Windows in combination with the opportunity Web-based applications provide, rather than giving customers the choice between one or the other. Microsoft calls this its "software-plus-services" strategy.

"Unlike Google, which is trying to take AJAX/browser apps and make them look like they're running on the desktop, Ozzie is making the point that the combined value of the Windows OS and assets on the Web -- including, but not limited to, [Windows] Azure and Windows Live -- is Microsoft's play, and a winning play at that," he said.

AJAX, or asynchronous Javascript plus XML, is a development language for creating interactive Web applications. Windows Azure, which Microsoft revealed at PDC, is its cloud-based application development environment that competes with Amazon's Elastic Compute Cloud.

Still, there is no denying Microsoft knows Windows must change as the industry moves away from running software on the client to using Web-based applications. The company's decision not to include Windows Photo Gallery, Windows Mail and Windows Movie Maker as part of Windows 7 in favor of Web-based versions of those applications is part of this trend.

Microsoft is even planning to release a hosted version of the Office productivity suite, which is Microsoft's top software seller next to Windows -- another acknowledgement of the move to hosted services, as well as a nod to competition from Google's Web-based productivity suite, Google Docs. Google Docs is beginning to gain some traction not only with consumers, but also enterprises.

Microsoft plans to release a lightweight hosted version of Office called Web Applications for Office around the same time it releases the next version of the productivity software code-named Office 14, Microsoft revealed at PDC.

Decisions to offer hosted Office and an overall thinner Windows client OS also are in line with the move to offer Windows on low-cost PCs in emerging markets that Microsoft is keen to reach. These PCs have less memory and CPU power, so they can't support an OS with a footprint as big as the premium version of Windows Vista.