Microsoft is planning to make its currently voluntary Windows anti-piracy program mandatory some time in the second half of 2005, company officials said on Wednesday.

So far, however, Microsoft has no timetable for broadening the program to other Microsoft products, such as Microsoft Office, server software or games, company officials said. But they did not rule out such an expansion at some point. And Microsoft representatives hinted that the company might also allow Microsoft partners to employ the Genuine Advantage methodology and techniques in the future.

The "Windows Genuine Advantage" initiative, which Microsoft launched in September 2004, is designed to check whether consumer and small-business customers are running legitimately licensed copies of Windows XP. Since September, about five million users have participated in the voluntary validation process, according to Microsoft officials.

Users validate by providing Microsoft-requested system information, including their Windows product keys, names of PC manufacturers, and operating system versions, which the Redmond software company uses to determine if customers are running legitimate copies of Windows. Microsoft officials have said that none of this information can be used to identify or contact individual users.

Microsoft has been testing the Genuine Advantage program on the Microsoft Download Center, where it has been requesting that users validate their copies of XP before obtaining certain Microsoft programs, patches and fixes for download. If users decided against validating, they still have been allowed to obtain the requested downloads.

But starting later this year, Microsoft will require users who want any of the Windows-client-related code from the Microsoft Download Cente and Windows Update sites to first validate their software as part of the Genuine Advantage program.

Microsoft has created a loophole for "customers who may require more time to move to genuine Windows software," however: For some undetermined amount of time, Microsoft will allow these users to obtain critical security updates only via the Microsoft Automatic Update site, even if they don't pass validation muster.

Microsoft's client team was surprised by how many users voluntarily opted into the pilot Genuine Advantage program, said David Lazar, director of Microsoft's Windows client product-management group.

"Typical opt-in program rates are five percent. We had over 60 percent," Lazar said. "Customers really want to know that they got what they paid for."

Lazar emphasized the security message of the Genuine Advantage program, as well. He said that pirate software could have viruses and back doors that could make them more vulnerable to potential attacks.

"Non-Genuine software doesn't provide customers with the peace of mind that Genuine software comes with," Lazar said.

Microsoft has been using software give-aways and discounts to incent participation, as well, Lazar said. On February 7, Microsoft is adding a few more incentives to the program, bringing the total value of discounted and free software offered for participating in the program from $390 to $450. Among the additional incentives: five more MSN Zone games and up to 30 percent off the $59.95 annual Microsoft Office Outlook Live e-mail subscription service that the company rolled out last week.

Microsoft also is adding 20 new language versions of XP and more Windows-related content to the pilot program on February 7, as well.

"I'm quite positive about this (Genuine Advantage program)," said Michael Cherry, a senior analyst with Directions on Microsoft, a Kirkland, Wash., analysis firm. It doesn't just help Microsoft; it also helps partners who are selling 'Genuine" Windows,' but having to compete against counterfeit or pirated versions."

Microsoft also has made no bones about the fact that it is looking to Genuine Advantage to grow Windows client revenues in a largely saturated market. Windows has cornered more than 90 percent of the desktop operating system market.