You can reset your Windows Vista activation by performing the following:
1. Click on the Start button and in the Start Search box type in: slui.exe 4
2. Press the Enter key on your keyboard.
3. Select your Country.
4. Follow the instructions for phone activation.
5. Once completed, restart your computer.
6. Then visit http://www.microsoft.com/Genuine/ and click Validate Windows.
Please note: I am not a Microsoft employee...only a voluntary forum contributor.