But there's a gotcha.. I upgrade to 8.1 via Windows 8. The first step from Windows XP to 8 ran pretty smoothly, all of my data from the XP installation was moved to a folder called windows.old where it could be recovered from by someone with a basic understanding of PCs. All well and good, but the obvious next step was to upgrade to Windows 8.1.. a bit trickier as you can't do that without installing KB2871389 first (either through Windows Update or manually). The Windows 8.1 download is enormous, 3GB+ but it installs smoothly enough.
The catch? Well, upgrading from Windows XP to Windows 8 creates the windows.old folder with the old data in. Upgrading from Windows 8 to Windows 8.1 DELETES that folder and creates a new one with the old Windows 8 settings.. obliterating your original data from the Windows XP installation.
Well, that wasn't a problem for me as I'd backed up everything onto another drive which I unplugged to be on the safe side. But it wasn't what I was expecting to happen *at all*.. and you can see that a less paranoid customer (or one without a suitable backup disk) could well lose everything if going from XP to 8 to 8.1. And I do notice that there doesn't seem to be a Windows 8.1 Upgrade version available anywhere, so this is the path that a lot of people would take..