I ran windows updates. I ran all the anti-spyware that you suggested but I couldn't get rid of that Trojan downloader running in memory shown up by Ewido but uncleanable. Then I saw the advice from 'didom' to 'jabbyjab' who had exactly the same problem. I ran Fixwareout, which at first wouldn't run but has now done the trick.
I have to say that with the big cruel world the way it is to get so depressed about a virus seems pathetic, but I am a freelance writer and this PC is my livelihood. I know some of the evil ones who write these viruses must check out these forums - to them I say you made me very unhappy for weeks and it hurt - so you must feel great.
Now a selection of clever people at Geekstogo have helped remove the virus that I was starting to feel was actually running in my head. So thanks again.