Rolling Vista machine back to XP and Windows 2003

Going to strip Vista machine (Dell XPS 410) and install XP and Windows Office 2003. Will my Avast work on the changed system and what should I do to preserve my Avast and license.
Susan

Save your avast! licence file to a CD or Flash drive and remove your email from your post as spammers will harvest it!

Welcome to the forum. If you’re using the free version, you can simply register again after you install it
on the new OS.
If you have a license for a paid version that follow YoKenny’s advice.