Windows 7 (SeVeN) is probably going to continue the trial software trend that starts with Windows Vista’s rearm, that user can install Windows 7 without any product key for free usage of 30 days as evaluation period. During the 30-day activation free grace period, user does not need to activate Windows 7, and can use Windows 7 of any edition in full functionality.

Although Windows 7 product activation function will keep reminding user how many days left to input a product key and activate the system in order to continue using the operating system beyond 30 days. In reality, Windows 7 also equip with a secret ‘rearm’ key in order to reset the free 30-day evaluation period limitation, which allows user to extend the activation-free usage or evaluation expiry date of Windows 7 for another 30 days legally.

Best of all, Microsoft provides 3 times of available ‘rearm’ count, as part of tool for system administrator to reset and restore activation state of Windows 7 to factory state during initial OOB (out of box) grace period. So, by using the ‘rearm’ hack, user can reset and extend the activation grace period (aka evaluation trial period) for up to 3 times, effectively running Windows 7 without product key without activation for up to 120 days, or 4 months. The trick is, the rearm hack must be done only when the 30 days trial period or activation grace period is about to expire.

‘Rearm’ trick on Windows 7 is done using the similar commands and steps with Windows Vista. Follow these steps to reset and extend activation grace period from 30 days to 120 days in Windows 7:

1. Install Windows 7 without any product activation key.
2. After installation is completed, use the Windows 7 for 30 days and wait for the remaining days left to activate Windows counting down to 0, or almost zero.
3. When the activation grace period (or evaluation trial period) is almost expired or ended, log on to Windows 7 desktop, and open a Command Prompt window (i.e. type Cmd in Start Search and hit Enter).
4. Type any of the following commands into the command prompt, and then hit Enter:

   sysprep /generalize

   slmgr.vbs –rearm

   rundll32 slc.dll,SLReArmWindows

   slmgr /rearm

5. Reboot Windows 7 to enjoy another 30 days of free usage without worrying about activation nor even need to crack Windows 7.
6. When the activation grace period countdown timer almost running down to 0 again, repeat the ‘rearm’ trick to enjoy another 30 days of Windows 7 for free. User can run the rearm command for maximum of 3 times.

As rearm only works for 3 times, make sure the command is only been run when the 30 days countdown of evaluation period is almost expired.

http://www.mydigitallife.info/2008/11/06/how-to-rearm-and-extend-free-usage-activation-grace-period-of-windows-7-to-120-days/