I don't know about Avast and A-squared. I use AVG. All I knew was when
sitting at my desk not using the computer the HD was running as if was being
used (it was). That really bothered me until I found out what was causing
it.
AVG runs at a pre-determined time.

<guybannister58@aol.com> wrote in message
news:1180235978.504252.159780@q19g2000prn.googlegr oups.com...
> On May 24, 10:00 am, "Bob" <rob...@grande.net> wrote:
>> Several times I have caught my hard drive running, and could not find the
>> cause. I run CCleaner, Ad-Aware (full system scan) ect. Never could
>> determine the cause. Today, I was looking at my Control Panel, and
>> noticed
>> a icon Software Explorers. Clicking on that, it opened Windows Defender
>> (which was still scanning). Mystery solved. It proved to me that
>> Windows
>> Defender runs to do the job it was intended for, how well it works I have
>> no
>> idea, but it does run in the background. This info. is intended for
>> anyone
>> that is as mystified as I was.
>
> Doesn't Avast (and also A-squared) similarly always run in the
> background, slowly scanning the HD?
>
> What's the difference in this "background scan" and the "on-demand"
> scan? Speed? Depth/sensitivity of the scan?
>