Sounds like it's set to run scheduled scans at set times, eg a certain time of day, or at start up etc. Find the control for this and disable it. Just run a manual scan once a week (or monthly, or something). The reason for scanning is that sometimes stuff can slip through the shield if it's brand new and not on the definitions yet. It could then worm it's way into just about anything, but mostly they seem to like system files I think.Do update the def's frequently. Auto update is good. Sorry if this is a bit basic.