Windows 8.1

Windows 8.1 is an operating system by Microsoft. It is a free upgrade for existing Windows 8 users. It replaced Windows 8 and was succeeded by Windows 10 on 29 July 2015. This is the first version of 64-bit Windows to drop support for processors without CMPXCHG16b, PrefetchW and LAHF/SAHF, as running on these processors will result in a black screen with error code 0x5D. Despite that Windows 8.1 was marketed by Microsoft as an update for Windows 8, Microsoft's traditional support policy treats Windows 8.1 similar to previous Service Packs of Windows.

RTM

 * The Start button was brought back (although it still leads to the Metro start screen).
 * Computer is renamed to This PC.
 * Clicking the File Explorer icon in the taskbar takes you to This PC instead of Libraries, unlike in Windows 7 and 8. Additionally, Libraries is disabled by default, you can re-enable it by right-click on the navigation pane and choose "Show libraries" or "Show all folders".
 * User folders (Desktop, Documents, Downloads, Music, Pictures, Videos) added to This PC.
 * New customization options for the Start screen.
 * Redesigned PC Settings.
 * The price of the Windows 8 and 8.1 Media Center Pack changed to US$9.99 until it was discontinued on 30 October 2015.

Update 1 (on non-touch devices)

 * When you hover over the top of a Metro app, Windows shows a title bar with minimize and close buttons.
 * Right-clicking on the Start screen opens up a menu instead of the touch-oriented controls at the bottom.
 * You can pin Metro apps to the taskbar.
 * A power button has been added next to the search button on the start screen.