Activating OEM Windows
: Diagnostics Tracking Service (May 2015
KB2952664: Labeled a compatibility upgrade for upgrading Windows 7, its purpose is to “make improvements to the current operating system in order to ease the upgrade experience to the latest version of Windows”.
KB3021917: A compatibility update for Windows 7 which “performs diagnostics on the Windows system [..] to determine whether compatibility issues may be encountered when the latest Windows operating system is installed.
KB2990214: This update for Windows 7 enables systems to upgrade from the current operating system to a later version of Windows.
To gain space by removing hiberfil.sys file, in admin prompt:
powercfg.exe -h off