Windows XP Service Pack 3 will include some of Windows Vista's features, according to a leak from beta testers.
The details were leaked on the NeoSmart Technologies website.
Windows XP SP3 build 3205, which was released to testers on Sunday, includes four new features among the 1,000-plus fixes and patches that have been issued since XP2's debut three years ago, the site said.
Features back-ported from Vista, said NeoSmart, include Network Access Protection (NAP), an enterprise policy enforcement technology that inspects PCs before they access a network, then updates or blocks them if they don't meet specified security criteria.
Other additions range from a kernel module containing several encryption algorithms that can be accessed by third-party developers, to a new Windows activation tool that doesn't require users to enter a product key.
Microsoft had previously announced SP3 support for NAP, which is part of Windows Vista and will be included in the not-yet-finalised Windows Server 2008.
Windows XP SP3, which Microsoft has said will be released early in 2008, will be one more move to extend the lifespan of the six-year-old operating system. Last month, Microsoft gave Windows XP a five-month reprieve by pushing back the end of retail and OEM sales to 30 June, 2008.
And last week, Microsoft launched a new "get-legal" programme that lets companies purchase large quantities of Windows XP Professional licences through their usual resellers.
Microsoft was not immediately available for comment on the leak, or the new features touted by NeoSmart.