Using msconfig has not helped - when I go into autoexec batt I see a column of boxes which can be ticked or not as desired, but most of the boxes have no text beside them to identify the programme concerned.
Using the firewall admin functions I can see a list of programmes permitted to access thwe net - however all of them are normal items like IE, outlook express, windows update, all of which I want to be able to use. (Before reformatting etc I had no problems with any of these trying to connect without me asking).
I have a vague recollection of this being something to do with BT internet software reinstallation when it happened before.
I'll figure it out eventually.
Thanks for all the advice so far.