That tech was correct.

 

You should not run two resident AVs at the same time. They can conflict and decrease your protection.

I'd like to stress and expand upon Joe's wording, rather than that of the original "tech" person:

 

Having more than one resident anti-virus program running "can [cause a] conflict (by using 'double' the memory/resources, slowing your system/responses down, and perhaps even lead to instability --- which could 'crash' your system) and decrease your protection [as the two competing programs 'slug-it-out' to see who'll intercept the potential viruses)".

 

But I don't know if I'd go as far as to say they actually " cancel each other out" and that you were "never protected".

 

Thanks!  I appreciate your help.

Actually, you have no need to install two or more antivirus software on your system. It will slow down the performance of your computer. Certain like security suite they only allow one at a time to run. For example, when you have Mcafee Security Center. Once you installed Norton Internet Security, it will disable your Mcafee Security Center.

 

A good choice of antivirus I recommend would Kaspersky and Norton (but Norton drain a lot of resources).

 

In the same time, you can use online scanner to add extra virus detection. I myself I use Kaspersky Online Scanner and antivirus software I use Symantec Corporate Edition. I will be switching to Kaspersky soon.