When your computer gets a virus, it brings on many emotions and questions; what, when, how and why to mention a few. The computer has software, so how did the computer get a virus? How is this even possible?
What you have to keep in mind is that no matter if you paid for the software or took advantage of one of the many free anti-virus alternatives, no anti-virus is 100% effective against viruses. This is not by any fault of the company who programmed the software nor is it any fault of the user. The reason that it is not 100% is because the people out there who manufacture viruses are always challenging the software programmers who design the anti-virus software. Often times these malicious creators win the race between good and evil in the computing world.
So what can the user do to protect themselves? The fact that you have anti-virus software installed is the correct first step in fighting viruses. However, how do you utilize your software? Are you utilizing the software at all? Most all anti-virus software by default will update the software on a daily basis with no interaction by the user with the exception of having the computer powered on and logged in. On the flip side, many of them are not programmed by default to scan at any particular interval and if they are, it may be an interval that is not commensurate with the user's Internet browsing habits.
Consider changing the settings on your anti-virus software so that it scans twice per week or more. In fact, if you make a habit of leaving your computer on all day and night then you can schedule your software to scan more often and in the middle of the night so you are protected while sleeping. Also, be sure that your anti-virus "auto-protect" feature is turned on.
A small amount of discipline goes a long way when ensuring that you keep your computer safe from the horrors of the Internet. Anti-virus is much more effective when the user remains vigilant.