Thanks for the complement. Yes, I did safe boot, restore checkpoints and so on. I've also run Windows repair. I went down the route I did because making a dual boot was less hassle than trying to reinstall all the applications again. Fortunately I don't really have to do USB disks often so even though rebooting into different operating systems is a bind it would only be every few weeks. But obviously it would be so much easier not to have to do that.