Best free antivirus?

Ive had norton ever since I bought my computer but when they came out with the new version, they decided not to support the old, and to top it off they went up on the subscription service.
I'm looking for something that offers free updates and script blocking.
BTW I'm running windows xp.

any suggestions?

What are people doing? Honest question!
If people are doing the same things as my wife, they're installing software sent via email claiming to give them a different colour star next to their ebay id or something.