Several and Windows experts, including Brian Livingston, who publishes the Windows Secrets newsletter, have posted details on how to extend the 30-day grace period a maximum of three times, for 120 days. "All versions of Vista allow a 30-day period without activation, except the corporate-oriented Vista Enterprise, which supports only a three-day trial," said Livingston in the latest issue of his . "If you know the secret, however, you can extend the activation deadline of editions such as Vista Home Premium and Vista Business up to four months past the original install date."

The one-line command of "slmgr -rearm" changes the activation deadline to 30 after the current date, Livingston said.

A Microsoft spokeswoman confirmed the feature and command on Friday. "Yes, 'rearm' can be run up to three times from the release media from Microsoft," she said in an e-mail response to some questions. "This means [that] a total of 120 days total time is available as a grace period to customers that take advantage of rearm."

Microsoft has documented this option on its Vista Volume Activation 2.0 . Although the bulk of the technical information posted is aimed at corporate administrators, the sections dealing with repeated activation also apply to consumer users of the operating system.

Extending the grace period, the spokeswoman continued, is not a violation of the Vista End User License Agreement (EULA). Microsoft introduced product activation in 2001's Office XP and next used it in that year's Windows XP. The feature was toughened up for Vista, however; after the grace periods, nonactivated PCs running Vista drop into what Microsoft calls "reduced functionality" mode. In reduced mode, users can only browse the Web with Internet Explorer, and then only for an hour before being forced to again log on.