Rearming Windows Vista is a genuine and legal process to prolong the Initial Grace period of the operating system. Windows Vista has five different license graces: Licensed, Initial Grace (OOB), Non-Genuine Grace, Out-of-Tolerance Grace, and Unlicensed. The license graces are the status of the operating system in relation to the licensing, activation and validation processes. The Initial Grace or OOB licensing tag defines a copy of Vista that has not yet been activated.

Following installation, Microsoft enables users to use Vista for up to 30 days without activation. In the 30 days Initial Grace, Windows Vista is fully functional. The only interference the user will get comes from periodical activation notifications. The activation prompts will grow in frequency as Vista approaches the 30 day limit of the Initial Grace.

If the users fail to activate Vista by the end of the Initial Grace, the operating system will expire and will move into reduced functionality mode, delivering just one hour a day of browser functionality, necessary for the activation.

However, the Redmond Company also permits users to rearm Windows Vista. Rearming the operating system means that by the end of the Initial Grace, the users can return the activation timer to zero and benefit from another 30 days of testing. This can be done via the Software Licensing ManaGeR integrated into Windows Vista.

"Initial Grace (or OOB Grace) starts the first time you start your computer after you install the operating system. It provides 30 days for the computer to be activated. The Initial Grace period can only be restarted by running sysprep /generalize, or by using slmgr.vbs -rearm. These processes reset the Initial Grace timer to 30 days. This will only work three times," reveals Microsoft.

In order to rearm Windows Vista, you simply have to enter slmgr.vbs -rearm in the command prompt window.