Yesterday - I tried turning my 'puter off - my big black Acer box... using 'install updates' and there it hung... 'installing updates 1 of 3...' 20 minutes passed then an hour, two hours, then eight before I lost patience and pulled the plug on it. Did a 'Safe boot' - couldn't see anything wrong - went to a last restore point. Told it was corrupted - couldn't be used. An earlier point worked...
What was causing the frozen/hung shut down? It looks like it was the .NET extension for the firefox browser - Microsoft Update Quietly Installs Firefox Extension. Of course I haven't let that extension anywhere near firefox - and I've two year's worth of log saying how it's failed to install, it looks like this was one fail too many and it decided to have a massive sulk about it.
Now I need to find out how to stop Windows trying to do updates for things I expressly do not want.
Oh the irony - the 2nd update on the list is supposedly a fix so you can remove the 'one-click' update from firefox.
Remove the Microsoft .NET Framework Assistant (ClickOnce) Firefox Extension.