Microsoft wants to release its Longhorn client operating system in 2006 in order to "appease" the customers that have bought into its Software Assurance (SA) licensing package, according to analyst Gartner.

Last week Microsoft said it would remove its new file storage system, WinFS, from the next version of the Windows client, code-named Longhorn, so that it can release the Longhorn client operating system in 2006.

But while the client may arrive earlier than thought, the Longhorn server operating system is still not expected until 2007.

Gartner said in a statement: "Gartner believes that 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.

"Microsoft's earlier assertions that Longhorn was not a date-driven release no longer seem accurate."

The analyst added that the updated Windows XP and Longhorn without WinFS would "not be generally available" before the second half of 2006.

And Ovum predicted that the significance of the Longhorn release would be much reduced by the absence of WinFS. "Clearly, the desire to get out the software in 2006 has required compromise at the highest levels of the company," the analyst firm said in a statement.

Gartner advised that users should standardise new PCs on Windows XP Service Pack 2.

It added that when Microsoft offered more information on the timing and benefits of Longhorn and WinFS, companies running XP would have an up-to-date, fully supported operating system and would be able to choose between adopting the first Longhorn release or waiting for the release that includes WinFS.

But Gartner warned that companies should not make strategic plans based on the immediate availability of WinFS.

Microsoft Windows XP marketing manager David Weeks said the software giant had listened to customers' views on Longhorn and heard they wanted improved user productivity, easier deployment, increased reliability and enhanced security.

"We've had to make some trade-offs to deliver the features [that] corporate customers, consumers and OEMs are asking for in a reasonable timeframe," he said.

"Software Assurance for the Windows client is the best way to stay up to date with the latest and most advanced OS software from Microsoft.

"Enterprise Agreement and SA customers will get any and all product updates that are shipped during the life of their agreement."