There’s a simple command-line tool that will allow you to extend your activation so that you can use
Windows for a full 120 days without activating it. The Windows Software Licensing Management Tool is the Visual Basic script slmgr.vbs, found in C:\Windows\system32. To run it , start a command prompt as an administrator by typing cmd in the Search box and right clicking the icon that appears at the top of the Start menu and selecting “Run as administrator.” At the command prompt, type this command and press Enter:
You’ll see the message, “Command completed successfully. Please restart the system for the changes to take effect.” Reboot, and your activation period will be extended for 30 additional days. You’ll be able to do this three times, which means you’ll be able to run Vista without activation for 120 days.
After you type in your commands, nothing will seem to happen for a while, perhaps a minute or more. Do not worry; nothing is wrong. slmgr.vbs take a while to go about doing its business. After you reboot, you can check whether your time was extended using slmgr.vbs to report on the state of your system’s activation. Type this command and press Enter:
A screen appears telling you how long you have to wait until you have to activate Windows.
Several people have reported that you can put off activation for a year or more, using a Registry hack. On a PC that has yet to have Windows activated, open the Registry Editor, and go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\SL. Look for the key named SkipRearm and change the value from 00000000 to 00000001. Exit the Registry, then use the slmgr command as described earlier to push out the activation deadline 30 days. You may now be able to keep doing this indefinitely. There’s a chance that Microsoft will close this hack off, by the way, and it may be short-lived.