Thank you very much for the response......
My reasoning for the approach is this......many security suites such as CA which I use, as well as a different one my daughter uses, provide a "vault" where you can store critical data values that you don't want to transmit, either from mail, when browsing the web, or from messaging applications. Depending on the setting, they can simnply replace the secured data with asterisks or provide you a prompt to allow or disallow sending of the information.
And since multiple firewalls running at the same time can cause conflicts, excessive slowdown and other problems, it's best not to do this.
But Avast has often picked up viruses that other applications miss, and vice versa, so it's handy to have it on hand for an on demand check. For example, I was having a problem with some trojan that was preventing me from getting to security sites (not Conflicker, it turned out). It also prevented the Microsoft MSRT tool and Spybot from running. Merely changing the name of the Spybot executable allowed it to run and find a couple of items that had been missed by other scanners.
After that was fixed, MSRT was able to run and it found still one other item that others missed (Aleuron-C).
It's really impossible for everyone to catch every new piece of malware immediately, so running multiple ones on demand very often will pick up things that a single A/V application misses.
Thanks again for the response....