What you need to do is to reactivate your Windows Vista installation using the telephone activation method:
You can get started with phone activation by typing "slui.exe 4"
(w/o the quotes) in the Start Search box in the Start Menu and pressing
Enter.
The phone activation process takes about 6 minutes.
In addition, please review the following:
You may be prompted to activate Windows Vista on a computer on which Windows Vista was already activated by a Volume License or OEM installation: http://support.microsoft.com/kb/931573