Does anyone know of any free anti-virus software for Windows XP, specifically, (not thirty day trials or anything like that) that they would recommend? If I had my druthers, it would be open source because I have some modifications in mind, but I might take anything that happened to be free.

I've become sufficiently annoyed with Norton, McCaffee, et. al. in combination with startup methodologies, interference with certain firmware things I'd like to do locally that I've uninstalled all AV software on my machines at home. While not having any AV software isn't really a source of any worry/concern to me, I would like to get my hands on some. I'm designing a system for my home that will eventually be relatively sophisticated and might generate interest from other people, and so I'd like to build some AV into what I'm doing.

It is not essential that I be able to distribute it as part of some package/image, though that would be cool. Without recommendations, I'm simply going to try out various ones to see if they're to my liking, but I thought getting a tip might save some time.

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"Government big enough to supply everything you need is big enough to take everything you have... The course of history shows that as a government grows, liberty decreases."

-Thomas Jefferson