I have scanned with AdwCleaner and nothing was found.
No full scan has found anything suspicious.
Thinking back, I received an email which I thought/think was from my central heating oil supplier with an Invoice attached, when I tried to open it , I had the pop up warning and I deleted the email.
The warnings started the same day.
The email is not in my deleted emails file, I assume the whole thing could be in the Vault.
I am now thinking that this was a legitimate email and this is a "false positive", but as I can't find the email , I am unable to report the details.
As you have probably realised I am not totally PC competent, so I am reluctant to poke about too deeply into my PC, or go into any convoluted (to me) possible solutions.
Is there any other way I can stop the pop up reports ?
I have tried uninstalling Avast and reinstalling it, but this made no difference.