Recurring false start

Good morning.
My wife's laptop (Vista Home Premium) last showed the computer adding updates 1, 2 and 3 which it then configured.
It switched itself off after configuration.
Now, when started, the computer opens in the page Configuring updates stage 3 of 3. 0% complete. Do not turn off your computer.
This repeats et al.
I have tried F12 (Windows error recovery) with Safe Mode etc. Nothing works; the computer restarts and goes to Confiuring updates.......etc.
As a last resort, I have been told, I will have to reinstal Home Premium, but this will lose some items that were not backed up in time.
However, I have also been told that - if I catch it in time - I can press a button which will prevent the reinstallation overwriting the bits I want to save.
Please, any ideas, anyone?

Welcome
If I understand correctly, your big concern is to save your stuff.
If you try this you may be able to save your stuff, then we will have more methods to get you up and running again.
Use Ubuntu Live CD to Backup Files from Your Dead Windows Computer - How-To Geek
I think that what you refer to in the last sentence of your post is a repair install. We may have to resort to that, but best to have your stuff backed up first.

Many thanks for your kind reply.
I have to sort some other things out now and will have to come back to my problems - and your answer - tomorrow.
Kind regards.
Granjay.

What happens if you just let it go for 10 or 15 minutes or is it restarting before it completes? The last part is not clear to me.