Avast para outro sistema operacional

Hi friends use avast on my XP notebook as I want to use Avast on Windows 8 in the same notebook as I transfer to another operating system.

Do you mean the free or the paid version?

Inserting the license key into: Avast Free Antivirus.
Resend purchased license: http://www.avast.com/en-eu/resend-license-paid.php
Or, for free, re-register Avast.