


Most antivirus programs do not allow access to those options precisely for this reason. In the most extreme example, I once saw a client's machine take over half an hour just to boot to the desktop. Doing so means that it can bring a machine to a crawl. Some people feel that having the software scan files at all stages of file operation is advisable and necessary. Just like what Norton Antivirus allowed people to do about a decade ago (which is what soured people against their software), Avast can be set to scan files each time they are accessed, created, edited, deleted, or closed or some combination of these various file operations. To answer your question directly, yes, Avast can slow down your machine as it can be set up incorrectly to do more scans than are necessary. The programs that I recommend and sell to my clients at this point is Kaspersky Antivirus. I have been in the computer sales and service field for over 25 years and must say that I have found Avast to be one of the worst antivirus programs on the market, surpassed only by AVG in its ineptitude.
