Although the registry key has been set on my computer, I realised that the expected Microsoft updates had not come through - they were due on Windows 7 computers yesterday or first thing this morning. I found via Control Panel - Windows Update that the update process is not running. Although a restart was advised that had no effect.
I contacted my local computer shop and I'm going to have to take the computer in to them to get this sorted out.
This is likely to be the same for many people.
It's clear that this is considerably worse than the so called Millenium bug.