A Microsoft official said the company does not plan to release Service Pack 3 for the Embedded version of Windows XP in April and would say only that the update will come "at a later date."

Microsoft manager Chris Keroack, in a forum post Monday, also said the company does not yet have a definite date for releasing SP3 for Windows Fundamentals.

SP3 for "XP Embedded and Windows Fundamentals will be available at a later date," wrote Keroack, in response to a question that asked whether either would be available by the April 29 release date that Microsoft has set for the standard editions of Windows XP SP3.

Windows XP Embedded is widely used as a built-in operating system for computerized electronics devices such as TV set top boxes and point-of-sale terminals. Windows Fundamentals is a slimmed down version of XP tailored for use on older PCs.

Microsoft on Monday said it has finished work on XP SP3, the third and final service pack for the Windows XP operating system, and that the update will be available for public download on April 29.

Windows XP, Service Pack 3, will be released to Microsoft business customers through their MSDN and TechNet subscriptions sooner than that -- but Microsoft didn't provide a specific timetable.

The service pack should offer a number of enhancements over the current version of the OS. It includes all updates issued since Windows XP Service Pack 2 was released in 2004, and some new elements.

Among them: A feature called Network Access Protection that's borrowed from the newer Windows Vista operating system. NAP automatically validates a computer's health, ensuring that it's free of bugs and viruses before allowing it access to a network.

Windows XP SP3 also includes improved "black hole" router detection -- a feature that automatically detects routers that are silently discarding packets. In XP SP3, the feature is turned on by default, according to Microsoft.

Additionally, Windows XP SP3 steals a page from Vista's product activation model, meaning that product keys for each copy of the operating system don't need to be entered during setup. The feature should prove popular with corporate IT managers, who often need to oversee hundreds, or even thousands, of operating system installations.