The only "pirate-friendly" AV you can use is Clamwin, a free and open source project based on the Clam Antivirus project:
www.clamwin.com
However, it doesn't have a resident "stand watch" shield, so It doesn't catch viruses with their pants down. You should have to manually scan it yourself.
I use that for my Windows 2000 computer. It's not my main computer where I do my important stuff; it's what I use for backup, job search, and nothing really personal. It's a guest computer if a guest comes in to my apartment and doesn't have a laptop. It's an "unimportant" computer, but that's where I use Clamwin on.
Anyhow, there are free updates, program-wise and virus-wise, but you
will have to use those definitions to scan the objects
yourself, and
manually. But because everything is manual, it won't lock up your computer if you're sure the file doesn't pose a threat. Essentially, it won't argue with you.
Use it if you don't fancy the major players or the free editions and their invasive lock-downs.
Hope this helps.
EDIT: Other than that, I use Comodo Internet Security the free version on my main computer, the one that combines a firewall and an antivirus. It's pretty good actually.
