Developers always have been the target audience for Microsoft's Professional Developers Conference (PDC). Going into PDC 2005, the company's message isn't wavering. It is, however, expanding.

Microsoft is seeking to grow substantially the group it defines as "developers" by making available to them new tools and interfaces that it is hoping to convince them to use in building their next-gen applications.

The traditional Microsoft Windows and Visual Studio developers are still squarely in Redmond's sights. But now, so too, are Office developers, MSN Virtual Earth developers, MSN Messenger developers, and professional graphics developers.

Can Microsoft build momentum around these other developer constituencies, without neglecting its tried but true developer audience? And from where will these additional developers emerge? Will we see Apple switchers, Adobe and Macromedia refugees and Google groupies suddenly get the .Net religion? Or will Microsoft find a way to attract, train and win over a whole new audience, namely, individuals who never considered themselves developers before?

Those questions will be top of mind for me as Chairman Bill Gates, Windows VP Jim Allchin and Office honcho Steven Sinofsky outline Microsoft's future strategies at the sold-out Los Angeles confab.

The least common denominator on which Microsoft is counting to appeal to all of these groups is Windows Vista. Microsoft execs are expected this week to distribute a new post-Beta-1 Vista build (rumored to be 1592) to attendees.

Officials are set to show off more of the Vista user interface, possibly including the prodigal "Sidebar" task pane, according to sources. And execs are on tap to expound upon not only the existing Vista pillars, like the Windows Communication Foundation (a k a, Indigo) and Windows Presentation Foundation (Avalon), but also one new one, Windows Workflow Foundation, sources close to the company say.

Visual Studio 2005 "Whidbey" will get plenty of mentions, too. But on the tools front, it sounds as if Microsoft is planning to play up more heavily its Whidbey follow-on, code-named "Orcas." Microsoft execs are expected to talk publicly about the pending Visual Basic release (which seems to be getting a big shot in the arm from the FoxPro team), Visual C# 3.0, and a new query framework add-on at this week's PDC.

Unlike the case with recent PDCs, at this year's event, Office is set to get almost as much time and attention as Windows. Microsoft isn't yet ready to hand out Beta 1 of Office 12, but it is set to do some Office 12 show and tell at the PDC. We're expecting we'll even hear about at least some of the new Office 12 servers that will make use of SharePoint Services.

Future releases of Visual Studio Tools for Office, a set of development tools and technologies for folks interested in building applications on top of Office, are going to be prominent on the PDC docket, as well.

I'm not expecting any Sparkle bits to be part of 30 gigabytes worth of PDC software that Microsoft is promising to PDC attendees. But word is Microsoft finally will demo its Sparkle "Flash killer" at this week's show. Maybe we'll finally hear Microsoft explain its plans for its full "Expression Studio" suite of professional-graphics tools, as well.

Given this line up, Microsoft officials have a few challenges on their hands. They need to deliver on the "shock and awe" hype, especially around Vista and Office 12, they've been generating around this year's PDC. They need to present their myriad messages in a way that doesn't confound their current and intended developer audiences. And they need to clarify which Microsoft tools and platforms are targeted at which developer camps.

I wouldn't be surprised to see CEO Steve Ballmer's new rallying cry become "more developers, more developers, more developers!" (rather than just "developers, developers, developers!) in the not-too-distant future. But will programmers of all stripes heed the Microsoft call?

What's your take? Has Microsoft got a solid story for more than just its core .Net developer base? Those of you attending this week's PDC (and those not), weigh in. Talk back below or write me at mswatch@ziffdavis.com and
let me know what you think.