The company on Tuesday released to the public Windows XP Service Pack 3, Release Candidate 2 Refresh.
Microsoft said the latest beta version of XP SP3 adds support for the HD Audio high-definition audio format and fixes some issues with the Windows Update service, from which the software can be downloaded.
But the company is warning would-be users that XP SP3 is still in trial mode. "While this update is available for anyone, remember that it is pre-release software," said Microsoft's Chris Keroack, in a forum post Tuesday.
The service pack "is time-limited, and is intended for IT professionals, developers, and other technically inclined individuals that are comfortable using pre-release software," Keroack added.
Microsoft said it expects to roll out a final version of Windows XP SP3 in the first half of 2008.
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.
Windows XP SP 3 also 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.
Microsoft is in a bit of a Catch-22 with XP. The more it strengthens the OS, the less reason users have to upgrade to Vista, which by many accounts has failed to catch on with computer users in both the home and office since it debuted last year.
Microsoft recently released Windows Vista Service Pack 1 -- which includes more than 300 hot fixes designed to improve the operating system's speed, security, and stability. Many users, however, have complained that installation of Vista SP1 on their systems caused numerous problems.