Thank you for your prompt replies. I’d like to ask more please:-

If the problem “is that you don’t know how things are working”, which I accept. Can you suggest how or why the number of files on my PC has increased by almost 800,000 in 11 days? I’ve upgraded existing software, but neither installed anything new nor imported masses of files? (This PC is over a year old, so should be relatively stable). If we can’t explain it, we’re left with the most plausible theses, either that avast’s reporting is wrong, or that avast checks a varying number of files, and, perhaps, when it checks the smaller number, the check is incomplete. There is a last possibility, that in the second scan, avast checks 800,000 files twice, so that would not be a problem beyond a waste of time.

I’d like to ask about the second contributor to the topic, who asked me to trust avast: Don’t we have anti-virus precisely because we don’t trust suppliers completely? I’d suggest that skepticism is a healthy attitude to the world in general and to computing in particular.

Thanks and regards, Nigel