Software counterfeiters pass on Vista preferring to pirate Windows XP, a Microsoft attorney has said, outlining a practice that echoes the leanings of the market.

While explaining the "Global Anti-Piracy Day" educational and enforcement effort, Bonnie MacNaughton, a senior attorney with the company, acknowledged that pirates prefer Windows XP over Vista.

"Historically, counterfeiters tend to focus on the 'n-1' version of software," MacNaughton said. "Because of the more robust anti-piracy and security features in Vista, most sophisticated piracy rings still continue to focus on XP. But that's changing over time."

That pirates have stuck with XP - which retains the bulk of the Windows operating system's market share - is "very consistent with what we've seen in counterfeiting in the past," said MacNaughton. "There's usually a lag of between one and two years [before they can] figure out how to replicate those anti-piracy and security features."

Counterfeiters currently copy Office 2003 rather than the newer Office 2007 for the same reasons, she said.

MacNaughton also touted the day's announcements of new initiatives and lawsuit filings scheduled to take place in 49 countries, ranging from Argentina to the US. "As counterfeiters have gotten more sophisticated, we have realised that this is not a situation that we can address alone," she said. "And we want to stress [today] the collaboration with Microsoft's partners and customers, and governments."

In the US, Microsoft filed 20 new lawsuits in federal court against software resellers that, according to the company's allegations, either sold pirated copies of Microsoft Windows XP Professional and Office or installed the counterfeit software on new PCs. Nine of the lawsuits were filed in California; two each were filed in Ohio, Oregon and Texas; and others were filed in Connecticut, Florida, Louisiana, Minnesota and New York.

MacNaughton also said that Microsoft was planning on another anti-piracy educational effort early next year to make sure that customers know Windows XP's lifespan is coming to an end. "We're expecting that counterfeiters will attempt to fill the void at XP's end of sales," she said.

Microsoft will halt Windows XP Professional sales to small mom-and-pop computer sellers after January 31, 2009. Larger computer manufacturers, such as Dell and HP, however, would be able to obtain XP media for "downgrades" from Vista Business and Vista Ultimate licenses through the end of July 2009.

Microsoft only recently said that it would extend shipments of XP to OEMs; previously, it had said it would stop the practice in January.

According to MacNaughton, Microsoft will roll out a campaign in early 2009 that will remind people of XP's demise and warn them that copies they obtain after those end-of-sale dates could be counterfeit.

Data compiled in August by a Florida developer of Windows performance metrics software showed that more than one-third of all new PCs are still downgraded to Windows XP from Vista, either by the user after purchase or by the computer maker at the factory.