The Windows Secrets newsletter has published step-by-step instructions for extending Windows 7's standard 30-day product activation grace period to a full 120 days, using a little-known command in a software licensing utility that comes with the operating system. That means people who can get their hands on downloadable versions of the operating system can avoid paying for four months.

Windows 7 won't be available to consumers until Oct. 22, but it's available now as a download to subscribers of Microsodt's MSDN and TechNet services for developers and tech professionals. The final version is also available on BitTorrent and file-sharing sites.

However, as Windows Secrets contributing editor Woody Leonhard notes, it's important to make sure the software is authentic if you don't go through official channels. He recommends following these instructions on Softpedia to make sure.

ComputerWorld says Microsoft has confirmed the ability to extend the trial period for Windows 7, and says it's not a violation of the end user license agreement that comes with the operating system. Windows Vista offered a similar capability.

As outlined by Leonhard in his story, the process resets the trial period to give the user another 30 days. Getting the full 120 days requires going through that reset process three times, at the end of each 30-day period. After the third time, the trick doesn't work anymore.