This is an older article which appeared in the Register-News.

Baseball Mom from our forums has a situation where her children ‘accidentally’ installed a second software on her home PC. This happens more and more every day as our kids grow up around technology and often know how to use computers and the Internet better than we do.

Can you do it? Probably. Some antivirus programs contain a check to see if there is other protection software present, and others do not. In this case, Norton did not check to see if there was protection present and installed itself.

Now, should you do it? In my opinion, nope. My reasoning is that the software will possibly ‘fight’ about which is actually supposed to be protecting the system. This can make for system resources being hogged by both programs that are attempting to do the same job. This amounts to your system performing double-duty on a task that should only require one or the other program to be active.

The second reason to not double-up on antivirus software is that you will have false positives and run the risk of one program destroying the other. Antivirus programs use definitions of viruses to check your PC and remove any bugs that might sneak in past your firewall (you are running one, aren’t you?).

If you have two antivirus programs keeping you protected, when one scans files it should find the definitions from the other software. This may result in a scary moment where you are advised you have a virus. You don’t, but the definition matches, and the program is not smart enough to know the definition is not a real virus. The false-virus is then deleted, making your first program less effective.

Later, your first program scans and finds the definitions from the second program. Again, you are told you have a virus, and delete the bad file. The end result is that neither works as it should, possibly leaving you even less protected since you think you are safe and may be a little more careless with your activity.

So, the short version is that you should not be running two antivirus programs. They will bog down valuable resources and work against each other, hurting you. What you should be doing, is using Windows’ Automatic Update, install a firewall, use an antivirus program (ONE), and not go to questionable sites.

Dan Voyles repairs PC’s professionally in addition to providing this column to the Register-News. He can be reached at askageek@register-news.com