But the software company confirmed that for its upcoming Windows Vista operating system, companies will be required to activate their software differently than they do today in order to prevent the leakage of volume licenses that are the source of most Windows piracy.

A ZDNet.com blogger reported earlier in the week on a conversation between a Windows user and a Microsoft support staffer, who allegedly admitted that users who refused to install the WGA update would be given 30 days before their copies of Windows would stop working.

ZDNet.com said that Microsoft refused to deny the report at the time. But later, Microsoft appeared to sing a different tune.

"No, Microsoft antipiracy technologies cannot and will not turn off your computer," said a spokeswoman with Waggener Edstrom, Microsoft's public relations firm. "The game is changing for counterfeiters. In Windows Vista, we are making it notably harder and less appealing to use counterfeit software, and we will work to make that a consistent experience with older versions of Windows as well."

Microsoft last fall began testing WGA as a way of trying to find pirated copies of Windows. In mid-June, it announced that users would need to download and pass WGA to be eligible to download the latest versions of add-on software such as Internet Explorer 7 and Windows Media Player 11. Users would still be able get the latest security updates, though. Companies that buy Windows XP through large package deals are exempt from having to install WGA.