seriously, if you have a pc and no antivirus its time for a wake-up call
first thing to do when you get a new computer is to put a decent antivirus on it
I recommend ESET
http://www.eset.com/
its has a firewall, a spam mail filter, a great antivirus (the only antivirus that doesnt need an exact virus signature to block a virus, this means it can block a virus that is a unrecorded variant of another virus)
i must warn you it is pretty expensive but you get what you pay for, it is completely automated and it uses very little system resources, it also gets about like 5 virus signature updates per day which is awesome, always up to date
i have had this program on my computer for about 8 months now and havent had a single virus yet, it has blocked many over that time
it constantly monitors any file that is incoming on your computer and will block it before anything bad happens it will close the connection and quarantine the item
On another note it will be fun to see what happens, about a couple weeks ago my ISP was under attack but a large army of "zombie" computers. This prevented anyone using Road Runner from accessing most websites as it messed with DNS adresses the solution BTW for those of you who might have experienced this problem is to use openDNS (google it)