Finally got round to finishing off the parents in law computer repair after their virus/adware/spam attack. The only thing that was wrong was that Norton Antivirus complained about not being able to run activex controls when you went to view its console. A search on google didn't really help much apart from saying that it was advisable to check that the autoupdate was running within services.msc.
I ran services.msc and got the same message which is *really* strange. I then discovered (when I accidentally clicked on my userid instead of theirs on the computer) that my logon account worked fine. I now knew that the problem was user related and not computer specific which was a good start - but where to start?
Searching online I came across a msdn article on url security zone templates so I had a read of that and spotted that the template zones are stored in HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Internet Settings \ Zones
An export from my user account and an import into their account and services.msc runs ok and more importantly so does NAV2002.
I exported the reg settings and brought them back and sure enough a lot of the settings were non zero (locked down) but I've no idea what they relate to, and at 10.35pm I don't really care.
The moral of the story is that when you set up a machine for someone, create your own clean username and password with admin priveledges and don't tell them what the password is as a clean user profile will solve lots of problems.