Peter Garstin wrote:My laptop refuses to start under 8.1 and also refuses to restore to a point before the update. Oi veh! And the other one ('er indoors') is still running XP.
I expect you've looked online for a solution Peter but if not this site may be of use. Alternatively you could reboot in safe mode and by a process of elimination you may find a programme that is causing your problem.
There's a chance that you may be infected with Ransomware, but if you haven't received a request for payment to unlock your files, probably unlikely. If you have a recent back up of your files it may be worth reloading the OS!
As for 'er indoors' best to keep offline unless you 'ring fence' the XP system by using a virtual computer or change to Ubuntu, or use a Government Computer, either way the XP system is getting more vulnerable by the day!
Edit for spelling mistake Ubuntu.
http://pcsupport.about.com/od/findbysymptom/tp/computer-wont-turn-on.htm