Rearming your Windows 7 will let it run freely for 120 days without activation

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:

1. 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".
2. At the command line, enter in "slmgr –rearm" without the quotations.
3. Restart Windows 7.

After the reboot, your counter will have reset back the 30 days.