How do you use more than one anti-virus program?

As you've said there is no single anti-virus program that you can run that will absolutely be guaranteed to catch every virus.

More so: even if you were able to run every anti-virus program known to man - there's still no guarantee that the combination will catch every virus. There's no single tool or combination of tools that will catch absolutely everything.

That's the education part.

The goal is not to run more than one to catch everything simply because you still can't know that you've caught everything.

The reason I and others keep telling you that no single tool (or combination of tools) will catch everything is to remind you that you are the weakest link and must remain on guard.

You can't just assume that your anti-malware tools - whatever they are and however many you run - will keep you completely safe. In fact, making that assumption will probably make you less safe. You need to be aware of your own behavior on the internet - things like opening attachments, visiting malicious web sites, allowing malicious downloads - and keep that all in mind as an important part of internet safety.

On top of having good anti-malware solutions of course.

So what can you do with respect to multiple anti-virus solutions?

You can have only one "real time" scan active at a time. That means only one anti-virus package can be scanning the files you save as you save them, your downloads as you download them, and your emails as you receive them. Any attempt to have two or more anti-virus tools trying to do this at the same time will likely cause slowness, conflict, crashes and most commonly false positives.

Since most of the major anti-virus tools enable real time scanning by default they will often check at setup time to see if other packages are installed. What they do varies, but it can range from nothing to dire warnings (that many people misinterpret as errors) to actually refusing to install.

Many tools will peacefully coexist, provided you have real-time scanning turned off in all but one.

Why, then, would you want more than one if it's not also scanning what's happening?

There are two approaches to using a second anti-virus program:

• You can run as many on-demand scans as you like. An on-demand scan scans not what's happening, but rather scans the files already on your hard disk. You might have program "A" scanning in real time, and then schedule program "B" to do a full scan of your hard disk every night. This way you get two (or more) different anti-virus programs monitoring your system on a daily basis.

• You can run an on-demand scan if you have a concern. Let's say you just downloaded something and your machine started "acting funny" - perhaps a virus that your real-time anti-virus software didn't catch. You can manually run on-demand scans from other anti-virus tools to see if perhaps that's the case.

So you can, in fact, run multiple anti-virus tools; you simply have to do it in the right way so they don't conflict with each other.

My recommendation?

1. Pick a good, primary anti-virus tool and have it monitor real time if you like. (As well as an anti-spyware tool and a firewall.) I'm not a fan of most all-in-one packages, so typically that means you'll be looking for individual programs.

2. Remember that no single tool or combination of tools can guarantee complete protection. You must still assume responsibility for your online safety by understanding what is and is not safe, and behaving accordingly online.

3. Don't worry about a second anti-virus program until or unless you suspect a problem has gotten past the much more important points 1. and 2. above.