Windows XP Service Pack 3 (SP3) has been released to around 15,000 testers, with Microsoft on track to deliver the final version in the first half of next year. The preview of the final major update to Windows XP comes days after Microsoft release candidate preview for Vista SP1.

Although XP SP3 is due in the first six months of 2008, Microsoft is not giving a specific date for its release and even concedes that the half-year window is not set in stone. "We are targeting [the first half of] 2008 for the release of XP SP3 RTM [release to manufacturing], though our timing will always be based on customer feedback as a first priority," said a company spokeswoman.

As with Vista SP1, Microsoft at some point will offer a Windows XP SP3 beta to anyone who wants it. That timetable, however, was just as iffy as the final release's, with availability set only as "a later date".

Microsoft has said little about what will be in Windows XP SP3, and in general has been reluctant to even mention the update as it publicises the progress of Vista SP1 in company blogs and regular communications with the press. Analysts have speculated that Microsoft, which has already made several XP-related concessions, including extending support for the aged OS and pushing the end of retail and OEM sales out five more months, wants to downplay SP3 to make sure it doesn't steal any more thunder from Windows Vista.

According to accounts published last month, XP SP3 will feature more than 1,000 hot fixes and patches that have been issued in the past three years, as well as at least four new features, some of which will be ports of Vista tools.

Windows XP debuted in October 2001 and was last updated as SP2 in August 2004.

Related articles:

Windows Vista SP1 brings 'insignificant' upgrade

Windows Vista review