This could be interpreted as a bold, visionary leap into a new computing paradigm, or as a cynical failover to the old ‘leverage Windows’ strategy as a means to rescue the company’s struggling MSN business.

Microsoft executives characterized the new plan as the latest in a sequence of strategic sea changes that started with Windows 1990 and continued through Internet Explorer in 1995 and .NET web services in 2000.

To be clear, while the message was software as services, we’re not talking about hosted versions of Office or Windows. We’re not talking about decoupling existing functionality from these products and offering it as an online service. We’re talking about ad-supported web services that can be functionally tied to Office and Windows, and which borrow those two brands.

Windows Live does look good though, even in beta form, judging from a demonstration conducted in San Francisco by Microsoft chairman Bill Gates, chief technical officer Ray Ozzie and a cadre of senior executives.

Windows Live, which can be found already at www.live.com, is an updated take on the personalized web portal concept, originally popularized by services like My Yahoo, which can incorporate web and desktop content, search and RSS feeds.

Company executives demonstrated the construction of such a portal, using search as a means to find web pages, RSS feeds, podcasts, images, and web services like weather forecasts or virus scans that Microsoft called Gadgets, to add to the page.

It can be also integrated with other updated Internet services, including the new Windows Live Mail, Windows Live Messenger and Windows Live Safety Center, all of which have entered beta testing.

Live Mail appears to be a modernized front-end for Hotmail that, like Windows Live, uses the AJAX (Asynchronous Javascript and XML) programming model and an adherence to web standards that enables features like drag-and-drop components. AJAX enables a slick user interface that works more like a desktop app than a typical web site. There are no tedious drop-down menus, submit buttons and refresh spamming required for the client side of the application to update its state.

Live Messenger, an updated version of MSN Messenger, features more ways to keep track of contacts and share information, through tighter integration with Microsoft’s back-end data and the Windows client itself.

For example, the new Messenger back-end will keep track of who has permission to access whose contact information, so the only contact information you need to keep updated is your own. That’s a concept already implemented by startups like Plaxo.

Users will also be able to create shared Windows folders, the contents of which would be automatically synchronized across the Internet with selected friends. You could use it to share sales spreadsheets with a coworker, or photographs with your granny.

Live Safety Center, judging from the brief demo, will be quite similar to other hosted single-scan antivirus and PC maintenance services – a try-before-you-buy version of the recently launched Windows OneCare Live security package.

The new local search and maps function seeks to outdo Google Maps for the sheer gosh-wow factor, judging from the demo, in which a cafe near San Francisco’s Transamerica Pyramid was located with hi-res aerial photographs.

Remember how cool it was to first be able to see your maps in the form of an aerial photograph, shot from an airplane, with Google Maps? Microsoft trumps that with rotating closer-range aerial views, presumably shot from a helicopter.

In sum, while Windows Live and its related services are in the main just updated and enhanced versions of existing services, it is the blurring of the line between the desktop and Internet that drew the most marketing rhetoric. Indeed, Mr Ozzie sounded worryingly similar to Sun Microsystems’ chief executive Scott McNealy’s the network is the computer mantra, with his own the Internet is the platform comments.

Microsoft also knows it treads a fine antitrust line whenever it offers products that could be perceived as leveraging its operating system monopoly to close down competitors, and executives were eager to address those concerns. In these new Live products, whenever a Microsoft API is used, that API is documented and open for third parties including rivals to use to create competing or complementary products, executives said.

Mr Ozzie also suggested that Microsoft will offer foundation services, like storage and relationship data repositories to third parties to build into their services, leveraging Microsoft’s massive economies of scale and cutting back on coding time.

Looked at as a series of updates and tie-ups between existing Microsoft services, Windows Live could appear to be evolutionary rather than revolutionary. But it is the packaging and the business model which is perhaps most revelatory.

Microsoft is taking a leaf from the Google/Yahoo playbook. The company’s adCenter program, which is expected to broadly resemble the keyword/context-based ad model, is a core component of Windows Live.

In many respects, all of the aforementioned Live services, including Office Live (see separate article), are a wrapper around a core search-advertising engine, Live Search and adCenter.

MSN, currently Microsoft’s flagship web service, saw its revenue grow a measly 1% in the most recently reported quarter, as a 20% rise in advertising revenue failed to substantially offset a 30% decline in access services revenue. While 20% growth seems decent enough, Microsoft executives recently said that it represented growth in display ads that was merely in-line with sector growth. Its search advertising business, they admitted, was poorer than expected.