After the changes, you'll only be able to access the iTunes Store on Apple TV (2nd generation) or later. Previous versions of iTunes will still be accessible on these operating systems, but purchases and downloads will no longer be available.
The same security changes affecting the first-gen Apple TV will also affect Windows XP and Vista machines.
There may not be a whole lot of nostalgic love out there for the original Apple TV, but hobbyists and jailbreakers might still find the set-top box useful.
Microsoft's mainstream support for Windows XP ended on April 14th, 2009, while extended support ended on April 8th, 2014.
The writing has been on the wall for the Apple TV first-generation for some time, mind. Yes, there are still people - and businesses - that are running Windows Vista and Windows XP, or are quite happy with their first-gen Apple TV.
Noted by The Verge, Windows XP and Vista PCs will no longer have access to the iTunes store starting May 25. In a fresh support document, Apple says this device is "an obsolete Apple product" and it will no longer work with iTunes. The need to download and store content is a thing of the past. In fact, Apple officially declared it obsolete/vintage in September of 2015. That same architecture has been adopted in all recent updates, up to and including the Apple TV 4K fifth-generation model that was released in September 2017.