Microsoft last week faced accusations of short-changing its Software Assurance customers following its decision to strip core features from the next major Windows client operating system, codenamed Longhorn.

The software giant said it would remove a new file storage system, WinFS, from Longhorn, so the client operating system could be delivered by its 2006 deadline. But the Longhorn server operating system is expected to stay on the previous schedule and arrive in 2007.

In a research note, analyst Ovum said that the removal of WinFS would reduce the significance of the 2006 Longhorn client release. Experts added that the move could delay related technologies such as Microsoft Business Framework (MBF), a set of developer tools to build on the .Net Framework.

Microsoft said Longhorn's two other core technologies, the new feature-rich 3D user interface codenamed Avalon, and the new communications system codenamed Indigo, will be available for Windows XP and Windows Server 2003 in 2006. As a result Longhorn's main attractions will be the WinFX API and new security features such as the Next Generation Secure Computing Base.

Analyst firm Gartner accused Microsoft of reducing the value of the product in order to hit the 2006 deadline. "Microsoft wishes to release a new version of Windows by year-end 2006 to shore up revenue and appease customers that paid for Software Assurance on the client OS under Enterprise, Open or Select agreements," said Gartner in a research note.

David Weeks, Microsoft Windows XP marketing manager, said firms wanted better user productivity, easier deployment, increased reliability and enhanced security. "Of the three major parts of Longhorn - Avalon, Indigo and WinFS - [WinFS] is very complicated, and so we had to make the decision not to release it in Longhorn," he said.

But Ovum analyst Philip Carnelley said that many of the new features being promoted for Longhorn involved the WinFS file system in some way. "What is Longhorn going to be if you take out this major plank?" he asked. "If you are a large firm with staff on XP this is not going to make you think of being an early adopter."

Microsoft product groups and software partners are working to build a number of new products on top of the MBF layer, including the Microsoft Business Portal, future releases of Visual Studio .Net and Microsoft's Code Green suite of business applications. WinFS is now due in 2007, according to Weeks, although a first beta version will be available to testers in 2006.

For the latest news for IT professionals, visit ITWeek.co.uk