Most machines running XP are unlikely to be able to handle Windows 10 well (if at all). Their device drivers won't be compatible, their processors won't be fast enough and they'll have insufficient RAM.
As I've written before, for the 'proper' price of Windows 10, you can buy a refurbished Windows 7 machine (which will be as good as new, with a completely fresh installation of the operating system) and then, if you so wish, upgrade it for free to Windows 10 - or save yourself the trouble and spend £89 on the model that's already got Windows 10 installed:
http://www.accomputerwarehouse.com/products/computing/refurbished-computers
(That's where I get my own computers, and those bought on behalf of friends, from. It's an excellent company).