Since there is no direct upgrade path from Windows XP to Windows 8.1 or even Windows 8, Microsoft has reacted to criticism by licensing a cut-down version of PC Mover and offering it to latter-day XP upgraders for free. It will only migrate three applications for you, but for most people, that’s probably enough.
The good news is that this version of PC Mover works with Windows 7 as well, so if you want to take the strategy of migrating people to $99 off-lease PCs running Windows 7, it will still help.
The linked article above criticized Microsoft for not developing its own migration tool, but that seems a bit harsh. I’ve used PC Mover before, and found it to be a very capable tool. I’d be surprised if Microsoft actually could do much better. And Microsoft has a history of licensing third-party tools anyway: Every disk defragmenter Microsoft has ever shipped was a cut-down version of something written by other companies.
Of course it’s best to rebuild machines from scratch–it will perform much faster that way–but when there’s a must-have program on an old PC and the installation media is long gone, PC Mover is about the only way to recover it and move it on. Most people probably don’t have much more than three programs in that category.