I apologize if I seemed overly-harsh in my earlier response.
Many viruses and worms spread by sending themselves out from an infected
computer to everyone in that person's contacts list. A system compromised
with Trojans can be used for all sorts of things, including orchestrated
denial-of-service attacks on websites, or the sending of spam- all without
the knowledge of the person using the infected computer. So connecting an
infected system to the internet does us ALL a disservice.
In my opinion, we all owe it to ourselves and to each other to have
up-to-date antivirus software installed and running.
This site attempts to compare and rate the effectiveness of the various
antivirus packages:
http://www.virusbtn.com/index.xml
This article compares four freeware antivirus packages:
http://www.pcworld.com/howto/article/0,aid,113462,00.asp
You may also find some helpful feedback in the alt.comp.anti-virus
newsgroup.
Regards,
Ian.