Thanks for the advice - I’ll take it and look forward to seeing the results. Just one thing: I’ve never edited the registry (and don’t know how to access it) - will I experience any problems if I don’t do this?

When you say perform a clean install of avast! I presume that you mean that I should first uninstall it? Sorry if this is a stupid question!

One other thought. I realise that if avast! is as good as I think it is, I will be able to forget about Norton. But will uninstalling Norton mean that I will have to pay again if I want to re-load it?

Thanks again for your help