Did you know that a command line utility exists to deal with issues of activation and licensing in Windows Vista? The command line utility is called the Windows Software Licensing Management Tool.
In order to access the tool, click Start and type cmd in the Instant Search bar. If you are not running as an administrator, right-click on the cmd.exe and choose Run as Administrator.
Next type slmgr.vbs in the command line and the Windows Scripting Host Tool displays all of the possible switches.
You can also install a new product key by using slmgr.vbs –ipk <Product Key> and then activate the new license by using the slmr.vbs –ato switch.
This scripting utility is easy to use. Give it a try.