How Does Product Activation Work?

In addition to entering a 25-character product key, Microsoft now requires you to activate your copy of Windows. Microsoft requires product activation for Windows Vista, Microsoft Office 2007, and most of their new or upgraded software. Windows Vista allows you 30 days of use before requiring activation. When the 30 days expires , if you haven't activated Windows, it won't let you log on until you activate it.

How does activation work?

Many of the components inside any computer have unique serial numbers that are routinely read by the operating system. The Install Windows wizard collects data about the hardware components of your computer as it installs drivers for the hardware you have installed in your system. It then creates an individually identifiable activation ID that it applies to your computer. When you activate Windows Vista, Windows sends your activation ID to Microsoft's databank , where the information is stored, and Microsoft's activation server "unlocks" (activates) your copy of Windows. (If your computer isn't connected to the Internet, you need to call Microsoft to send your activation ID.) Each time you reinstall Windows Vista, you must reactivate it, and Microsoft checks that the activation ID hasn't changed.

Note  

Product activation does not limit the number of times you can reinstall Windows Vista on a single machine.

You can't install the same copy of Windows Vista on several different computers, because they have different hardware serial numbers. If you try, when the activation ID is checked against your original activation ID, they won't match, so Microsoft won't allow you to activate Windows Vista. This is how Microsoft's product activation prevents casual piracy. For example, if you forget about activation and loan your copy of Windows Vista to a friend, when he installs it on his computer it will create a different activation ID. The problems will begin when your friend tries to activate Windows on his computer and this new activation ID does not match the activation ID of the previously installed version. Even after Windows is activated, you can run into trouble, because Windows periodically checks the activation ID with the activation servers at Microsoft. (Yes, your computer will periodically report to Microsoft's activation servers, and no, you will not be asked permission beforehand.)