Microsoft is considering an update of Windows XP before the release of Longhorn, its next scheduled overhaul of the operating system still in early development stages.

Issuing an update to XP would represent a significant shift for the software maker, which for months has insisted that it had no plans to create a separate version of Windows before Longhorn. A company executive confirmed to CNET News.com on Thursday that Microsoft is now discussing an update internally referred to as "Windows XP Reloaded."

An upgrade would follow Windows XP Service Pack 2, a security-oriented upgrade that is slated to arrive before midyear. The features that would be included in an update are still under discussion, Windows lead product manager Greg Sullivan said in an interview.

"Calling it an interim release is overstating the current plan," Sullivan said. "We are exploring ways to add value to Windows XP."

However, Directions on Microsoft analyst Rob Helm said that any new version of Windows is likely to slow Longhorn's arrival.

"There's one Windows team and there's one core group of people (developing it)," Helm said. "If they do plan an interim release, it will have an impact on the schedule. How much will depend on what's in it."

Helm said that Windows XP Reloaded sounds like what he would term an interim release. "To my mind, a service pack with features that has the potential to impact compatibility is an interim release."

Helm did say that one option available to Microsoft is to try and boost some of the surrounding programs that are bundled with Windows while making fewer changes to the core OS. Such a "feature pack" could mean less of a delay.

In addition to adding further question to the already uncertain timing of Longhorn, Helm said Microsoft's constantly changing release schedule makes it harder for customers to plan.

"In the consumer market it's less important, but in the enterprise market, it's really important for Microsoft to provide a roadmap--and not just of major big-bang releases, but also of service packs. Right now that road map is still pretty hazy."

Executives have said for some time that there was no major release of Windows planned before Longhorn, including senior vice president Will Poole, who said last at last May's Windows Hardware Engineering Conference, "Don't expect an interim release."

Poole said at that time that Longhorn would ship in 2005. Microsoft later backed away from that date, saying only that it would ship when it is ready. However, until now, Microsoft has reiterated that no new versions of Windows were planned before Longhorn.

The release of Longhorn is seen as critical for Microsoft, with the company having tied new versions of Office and much of its server software to coincide with the new OS, which Chairman Bill Gates has called the biggest advance since Windows 95.

Sullivan said that the possible release of XP Reloaded does not indicate a delay for Longhorn. Microsoft has not said when that OS will ship, but analysts have said they expect it in late 2005 or 2006.

It is too soon to say if any development resources will be needed for XP Reloaded beyond the current teams working on Windows XP maintenance, he added.

The move comes as Microsoft is looking for ways to ensure that existing Windows XP users upgrade to the more secure Service Pack 2 code base.

"We're very interested in having as many people as possible--new PC buyers and installed base--take advantage of the work we've done in SP 2."