Sorry, I didn't see your post before now.
It's back up and running, having pretty much re-installed Windows (it kept everything but the programs themselves, thank fuck). I've run into a few more problems, smaller but still irritating. Windows Update did it's thing and then undid it straight away - it rebooted, told me it couldn't apply the updates, so it was uninstalling them. It rebooted, said the same thing again, and rebooted again. I've also had the AMD driver crash at one point, when all I had open was the Mount & Blade Warband config window, so I'm trying the new 15.8 beta right now.
I know it's early days yet for Windows 10, but I think I might go running back to 7 if the problems persist.