In order for Microsoft to verify legitimate versions of Windows 7, users must activate their copies of the operating system within a finite time limit. On first inspection, that time limit appears to be 30 days, but as was the case with Windows Vista, there is a way to stretch that limit to nearly four months.
Like Windows Vista, the upcoming Windows 7 comes with a command line utility called the Software License Manager (slmgr.exe) that allows the user to issue "-rearm" switch that will reset the countdown timer back to 30 days. This command may be issued a maximum of three times. If a user issues this command at the end of each 30-day period for three times, he or she would be able to use Windows 7 unrestricted for up to 120 days.
The procedure to reset the countdown is identical to the process used for Windows Vista:
- Start the command line by clicking Start > All Programs > Accessories > Command Prompt (Run As Administrator) – or for a shortcut, hit the Windows Key + R and type "cmd".
- At the command line, enter in "slmgr –rearm" without the quotations.
- Restart Windows 7.
After the reboot, your counter will have reset back the 30 days.
Microsoft confirmed to Computerworld that this trick does indeed work. "This means [that] a total of 120 days total time is available as a grace period to customers that take advantage of -rearm," said a company spokeswoman.