Windows XP and Vista prevented from using iTunes Store on May 25, 2018

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Starting May 25, Apple will introduce security changes that prevent older Windows PCs from using the iTunes Store. If you have Windows XP or Vista PC, your computer is no longer supported by Microsoft, and you're not able to use the latest version of iTunes.

You can continue to use previous versions of iTunes on your Windows PC without support from Apple. However, you won't be able to make new purchases from the iTunes Store or redownload previous purchases on that computer.

After May 25, you'll need to use Windows 7 or later with the latest version of iTunes to make purchases from the iTunes Store and redownload previous purchases.

The latest version of iTunes is available for PCs running Windows 7 or later. Download the latest version at apple.com/itunes.

Source: About iTunes Store availability