I’m writing this column from Las Vegas, where Microsoft is wooing web designers and developers with a conference called Mix06. Internet Explorer 7 is on display, and so is Atlas, a JavaScript framework that enables smoother browser applications that fetch data in the background and update only the portion of a web page that has changed.

Microsoft is also showing off hybrid Windows and web applications built for the Windows Presentation Foundation – the part of Windows Vista that includes XAML, an XML language for defining rich graphical user interfaces.

During a keynote session, the BBC’s Ashley Highfield, director of New Media and Technology, described plans to make the corporation’s entire output available for download for seven days after each show is first broadcast. The demonstration client application looked superb, with a 3D programme selector, transparency effects, and video of broadcast quality or better, with bandwidth requirements mitigated by peer-to-peer downloads.

A further endorsement of Windows Vista came from an unlikely source. Marc Canter, a founder of Macromedia, told me that the Vista GUI is “finally something to one-up Apple”, and that Flash was “a toy at best” in comparison.

That statement strikes me as an exaggeration; but even so the signs are that the disgracefully delayed Internet Explorer 7 will be a decent browser, Windows Vista a worthwhile upgrade to Windows, and Atlas-enriched ASP.Net a solid and productive platform for web applications. Canter, by the way, is no Microsoft puppy; he heckled the keynote with a cry of “Where are the open APIs?”

Aber Whitcomb, chief technical officer of the MySpace social networking site, told delegates that MySpace with 65 million members is now the second-busiest site on the internet, pushing MSN into third place. MySpace runs on ASP.Net 2.0 and SQL Server 2005, making it hard to claim that the technology does not scale up.

That said, if you strip away the Las Vegas glitz, the core of Microsoft remains Windows rather than the internet. It is a divided company, with one half – let’s call it Microsoft 1 – working hard to keep companies hooked on Windows and Office, while Microsoft 2 puts energy into cross-platform web services.

A shining example of Microsoft 2 here at Mix06 is the work Kim Cameron is putting into federated and secure identity management, using a system called InfoCard, which will be part of Windows Vista and also available for Windows XP.

The goal is a safer internet where security no longer rests on usernames and passwords. Cameron understands and promotes cross-platform interoperability as fundamental to InfoCard’s chances of success.

The technology on display at Mix06 is compelling, including the new possibilities for rich internet-connected applications in Windows Vista. But developers of public-facing web applications must be wary of building in a dependency on Windows clients.

This is what will hold back XAML, and why Flash will continue to be more than just a toy.