Windows XP is no longer supported by Microsoft for security updates, so I personally wouldn't suggest getting a computer that uses it. If you buy newer equipment as well keep in mind that Windows XP initially came out in 2001, so you're looking at an operating system that is nearly 20 years old that you may not be able to use newer programs or physical products on.

New technology is being created and improved upon all the time and you always have a team of people working on making the latest and greatest stuff. So if you want to buy new equipment for recording you'd want to make sure it's something that would even work in Windows XP, and even then there's a really strong chance that if you buy equipment compatible with Windows XP, which will most likely be second-hand, that the manufacturer may no longer offer support for the product. This could mean that they might have removed drivers from the website or if something goes wrong with your audio interface, microphone, etc, the manufacturer may not be able to help you troubleshoot your issues due to the age of it. Or, another point is a computer that is going to have Windows XP on it won't have very good specs in general.

This is all just my personal opinion of course! I'd just go with Windows 10. Everyone has their operating system they really like and ones they dislike, but generally speaking Windows 10 is pretty good.

Cheers,
Ember