I am in the midst of rebuilding Win XP on my main machine - it is fun starting from the rescue disc when you haven't even got SP 2! Anyway, all now updated and I decided to go back to AVG insted of continuing to use Avast. Thus I downloaded the free AVG file that I originally got in about April. I used this file, heavily updated on new XP machine last week. This time, the whole thing gave up the ghost when approximately 6 Mb of data had been downloaded.
At 11.00 today, I downloaded a brand new version of the installation file and this has installed and updated perfectly.
P.P.