It worked!!! (PHEW) I started with the first post by TomFace and clicked on the link to the 'live installer'. It found it in my 'downloads'...clicked on it and followed instructions. Must admit bit scarey as 'things with red crosses' initially kept popping up on my screen saying stuff like I wasn't protected (!!!) - got told to shut down pc (had to do this twice) and after what seemed like ages (but probably no more than a minute or two) ..with the second restart all seems to be fine! Big green ticked 'you are protected' and no 'messages' in Home or bouncing ball in updates! THANK YOU ALL SO VERY MUCH for taking the time to help me.