„By default, Windows Vista can be installed, used and run without any license, product key or the need of activation for 30 days grace period, for purpose of trial or evaluation. Although Microsoft initially stressed that users should purchase a license with valid product key before the trial period expires, or else Windows Vista will lock into Reduced Functionality Mode. However, a „rearm“ method has long since been discovered to be able to extend, or reset the remaining time for activation to another fresh 30 days, for up to 3 times.
Now Microsoft has confirmed that Windows Vista can be used and run for 120 days or 4 months (3 rearms), and extending the activation grace period is not a violation of the Vista End User License Agreement (EULA). All versions of Vista include Windows Vista Ultimate allow a 30-day free period without activation, except the corporate-oriented Vista Enterprise, which supports only a three-day trial.
To extend, reset or restart the initial OOB grace period of Windows Vista to another 30 days, use the following steps:
Click on Vista Start button and key in Cmd in Start Search box.
Press on Ctrl-Shift-Enter to open Command Prompt with administrative credentials (equivalent to „Run as Administrator“).
In the Command Prompt, type the following command and press Enter when done: slmgr -rearm or you can use sysprep /generalize
Reboot the computer.
Rearm again when the remaining activation grace period timer counts down to 0 days.
Rearm option resets the computer’s activation timer and reinitializes some activation parameters. „