Norton gave me a free trial once. It suggested making a floppy backup disc, which I did. Once I did that my computer could not start up again. The only way was to use the backup, and that was corrupted from the start, though I did everything just as directed. I must have had a virus I didn't know about. I had to reboot the whole thing from my backup discs, so I lost everything. I reinstalled Norton, thinking that just the backup disc they recommended was corrupted. This time I didn't make a backup disc, since there was nothing to back up anyways. If I needed to start over, it was no big deal now anymore. I did have a number of important documents on floppies, but not near all of them.
After I installed the free Norton program again, the computer ran terribly. It was so slow that I could handwrite documents faster than type them on the computer. And that was just the word processor; Internet and other programs were impossibly slow. So I wiped the Norton program, and then rebooted again. And then the computer ran OK again. But Norton does not seem a possibility on this computer. I guess there is an incompatibility there.
Frankly, (actually, not so much frankly as tongue-in-cheek) I think the whole thing is a self-perpetuating thing. The anti-virus manufacturers are also the originators of the viruses, or have them on their payroll one way or another. Either that or Osama is behind it all. I just want to point the finger at somebody, because I can't afford the cost of keeping up with all the antivirus, antispam, anti-implant stuff.
I use the free version of Ad-Aware, the free AVG anti-virus (new, thanks to David), TrendMicro (online free virus check), and my own tedious scruples. That means that I don't open any attachments, even from my family, if I don't know what they are and if I did not expect them, even though they come through hotmail with its up-to-date antivirus program. Those that open automatically from Outlook are immediately responded to by me with a trip to TrendMicro, pronto.
My son needed LimeWire for a school project, and now that he is finished program I can't remove it, and always have to turn it off before I go on the I-net, or the traffic will always go two ways whether or not I know it.
Other than that, I have had great success in keeping viruses off, and when I do get one or more, I usually have not too much difficulty getting rid of them anymore, now that I know how to do it.
One great benefit from my system is that I have some very hard rules that my kids have to abide by to use the computer. If I start getting all kinds of popups, then there has to be a reason, which is usually that they have been to a site that dropped some cookies into my system. That is an infringement of the rules, and costs them the right to use the computer for a while. I have a pop-up blocker, and all I do is check that once in a while to see what and how many have been blocked. Funny thing about pop-up blockers is that the only pop-ups that it doesn't block is the pop-ups that advertise the blocking of pop-ups. Hmmm! Anyways, it works better than blocking certain kinds of sites, or using filters. There seems to be very few sites that don't plant cookies. Again, Hmmmm!