Originally published: 2010-04-19 on my old blog
I feel the need to follow up on a piece of playground gossip I overheard this afternoon. I overheard two people discussing how slowly their Microsoft Windows PC was running, despite having 3 different AntiVirus programs running.
In the vain hope that someone will read this advice, I'll explain why having 3 different AntiVirus programs running will only make things worse, not better.
Without going into too much detail, an AntiVirus program will scan files on your hard disk when they are accessed. Therefore one AntiVirus program will make your computer very slightly slower, but this downside
is greatly outweighed by the benefits that an (up-to-date) AntiVirus application will bring, protecting you from all sorts of nasty viruses and worms.
The problem comes when people install multiple AntiVirus programs to try to fix a slow or infected machine, in the belief that "more is better". So, as we know, AntiVirus programs scan our disks when files change. However two or more A/V programs begin to step on each others toes, the programs start to scan the files not only that you've accessed, but those that the other A/V programs have accessed, thus setting off a chain of events which will massively slow down your machine.
So, stick with a single AntiVirus program you trust, and most importantly, keep it up to date by downloading
new virus definitions on a regular basis. You might want a second program to scan for spyware or malware, but you'll only need one anti virus program.
Good, Free, AntiVirus programs for Windows include Avast and AVG. Don't click on, or install anything
that pops up on your screen unsolicited and promises to fix your machine for you!