SAN FRANCISCO —Microsoft will deliver in March early developer releases of two of the three key pillars of its next major version of Windows, code-named Longhorn.

These so-called "Community Technology Preview" (CTP) WinFX releases will be made available to developers next month, said Eric Rudder, Microsoft's senior vice president of servers and tools. Rudder made the announcement at the VSLive conference here during his Tuesday morning keynote.

Rudder said the WinFX CTP releases will "bring Indigo and Avalon" out together for the first time, pointing to the "Avalon" Windows presentation system and the "Indigo" communications subsystem. The releases will also include elements of the WinFX programming core that will comprise Longhorn.

In addition, the releases come with a new build of Visual Studio 2005, Microsoft's next-generation tool suite. Rudder did not specify whether the CTP build will include the Visual Studio 2005 Beta 2 bits, but Microsoft is slated to ship Visual Studio 2005 Beta 2 in late March, as well.

"Even if it's March 38th or 43rd, we will deliver it [the CTP] in March," Rudder said.

Avalon and Indigo are two of the three key pillars of Longhorn, which is due to ship in 2006. The third key Longhorn pillar is called "Fundamentals," and consists of the more mundane but necessary Windows functionality, including its security, manageability, and deployment infrastructure.

Rudder said Microsoft will make the WinFX CTP builds available to its Microsoft Developer Network (MSDN) subscribers, among other channels.

The forthcoming pair of WinFX CTP builds will be designed to run on Windows XP and Windows Server 2003, not on any of the early Longhorn builds that Microsoft began distributing last year. Microsoft's goal in distributing these WinFX CTP releases is to get developer feedback on Indigo before the company releases full-fledged betas of Avalon, Indigo and Longhorn, according to company officials.

Rudder used his Tuesday "Indigo Day" keynote at the show to demonstrate the kinds of coding advances that Microsoft's Indigo communications programming infrastructure will enable.

As Microsoft first detailed last fall at its Longhorn Professional Developers Conference (PDC), Indigo is meant to provide developers with an integrated set of security, messaging and transaction infrastructure that resides atop XML.

Rudder described Indigo as Microsoft's "unified programming model for rapidly building reliable, secure transactions." In a Microsoft-issued press release issued Tuesday, Microsoft called Indigo "the code name for Microsoft's next-generation Web services technology."

Rudder emphasized during his hour-long presentation that developers can start preparing for Indigo and other Longhorn technologies today.

"It really is time now to take a look at Visual Studio and WinFX," Rudder said.

Editor's Note: This story was updated to clarify that Microsoft intends to release the two CTP builds at the same time.