Ah, 2007: the days when Windows Vista was all the rage (or inducing rage), the Apple TV was brand new and music download stores were the hottest way to get the latest albums. Apple certainly remembers that year... and would like you to move on. The company has posted a support page warning that the iTunes Store will no longer work on Windows XP, Windows Vista and first-generation Apple TVs as of May 25th. iTunes itself will function, but new purchases and re-downloads are off limits. "Security changes" necessitate dropping these older platforms, Apple said.
The writing has been on the wall for a while. iTunes 12 already requires at least Windows 7, and a first-run Apple TV is very limited in what it can do (you aren't about to watch YouTube or stream Apple Music). However, this is the surest sign yet that Apple wants those with older devices to get with the times. While you're probably using something considerably newer if you're reading this, the cutoff might help you nudge a friend who's still clinging to an ancient PC.