With Windows Vista, Microsoft brought to the table an entirely overhauled activation architecture compared to Windows XP. Vista users had the possibility to install and test drive the operating system, without entering a product key. Deploying Vista without entering an activation code threw the operating system into a 30-day initial grace period. At the same time, Vista came with the Windows Software Licensing Management Tool. And via the slmgr.vbs, users had the possibility to prolong the grace period up to full 120 days, without ever entering a product key. The same is valid for Windows Vista Service Pack 1. On January 9, 2008, Microsoft made available to 15,000 testers the Windows Vista SP1 Release Candidate (RC) Refresh - Build 17128 via Microsoft update. In an email announcing the release, the company also described a method to install SP1 on a copy of Vista, by taking the product key out of the equation.

"Keys Beta keys will *not* be provided for Windows Vista Service Pack 1 RC release. Participants will need to have a valid volume license key, Windows Vista RTM key, or do a 30-day PID-less install by clicking next at the key dialog and you may re-arm. You may re-arm your system 3 times by completing the following steps: ￭ In order to run slmgr /rearm, open regedit.exe and navigate to HKLMSOFTWAREMicrosoftWindows NTCurrentVersionSL. Verify that value 'skiprearm' is set to '0'. If this value is non-zero, the re-arm function will not reset the system activation timers", reads an email sent by the Windows Beta Team to the 15,000 testers of Vista SP1 Build 17128.

In order to access slmgr.vbs, you will have to open a command prompt window with elevated privileges. In order to do so, enter "cmd" in the search box under the Start Menu and, then, right-click the highlighted result selecting "Run as administrator". Type "slmgr" and hit Enter in order to get a complete list with all the commands associated with slmgr.vbs. Vista SP1 or no Vista SP1, you can still use the "smlgr -rearm" command to reset the Initial grace period of the operating system back to zero. Do so when the operating system's grace period is close to expiration.

"After verifying that the 'skiprearm' registry value equals zero (0), run slmgr /rearm from an elevated command prompt. Wait for the notice that the process has completed. This can take a minute or two. Once complete, follow the prompt to shutdown the computer. Upon restart, the computer will be running in OOB Grace and will have another 30 days in which to activate. No other changes will be made to the system by this process", the Windows Beta Team added in the email.