Windows Anytime Upgrade

Windows Anytime Upgrade is a utility that facilitated upgrades across successive editions of Windows Vista and Windows 7.

Windows Vista
A prototype version of Windows Anytime Upgrade named Windows Activation is included in Windows Longhorn build 4093 with limited functionality. It has been re-branded as Windows Anytime Upgrade since Windows Vista build 5219.

Windows 7
In Windows 7, Microsoft made changes to Windows Anytime Upgrade to reduce the time to upgrade by pre-installing the components for the upgraded editions in the operating system and it no longer required Windows Anytime Upgrade discs and instead, it required the user to purchase a license for the edition that the user wanted to upgrade to.

Windows 8.x
In Windows 8 and Windows 8.1, the feature was re-branded as Add Features to Windows and was used to purchase an upgrade license for the Pro edition or to add Windows Media Center to an existing Pro installation. Support for Windows Anytime Upgrade on Windows 8.x was discontinued on 31 October 2015.

Windows 10 and later
Windows Anytime Upgrade has been deprecated and removed entirely since Windows 10 build 10114 in favor of the Change Product Key utility.