Vista click here (windows-vista-update.com)
You can activate either online or by phone. To activate online you need an Internet connection. Activating by phone requires interacting with an automated phone system.
To activate Windows on this computer, do the following:
Open Windows Activation by clicking the Start button Picture of the Start button, clicking Computer, clicking Properties, and then clicking Click here to activate Windows now. Administrator permission required If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
You can then select the method you want to use to activate.
Note If you chose to automatically activate Windows online when you set up your computer, automatic activation begins trying to activate your copy of Windows three days after you log on for the first time.
Or is this what you mean/want?
To check your Windows activation status, do the following:
1. Open System by clicking the Start button Picture of the Start button, clicking Control Panel, clicking System and Maintenance, and then clicking System.
2. Under Windows activation, you can view your activation status. You can also change your product key by clicking Change product key.