Windows 8 uses a new technology called Fast Start in order to start Windows quickly. When you perform a normal Windows 8 shutdown (using the Charms bar), the Fast Startup feature stores the kernel's current session (hibernate) , so the next time you start your computer, the Operating System loads quickly. This means that your system is reinitialized fully only when required by the operating system (e.g. when a hardware change detected) and not if you want you to fully shutdown your system for several reasons, e.g. to extend your battery's life or to boot from another media, etc.
Windows 8 Full Shutdown (How to)
In order to fully shutdown Windows 8, you have the following options:
OPTION 1: FULL Shutdown of Windows 8 using Charms Bar.
1. Put your mouse on the lower left side on the screen to open the 'Charms" bar'.
2. Click Settings.
3. Click Power & while holding the SHIFT key down press Shutdown.
OPTION 2: FULL Shutdown of Windows 8 using command prompt.
2. Open Command Prompt (cmd) with administrative privileges. To do that:
3. Inside command prompt window, type the following command & press Enter:
shutdown /s /f /t 0
The above command makes Windows to shutdown completely. If you want to perform a system restart after fully shutting down Windows 8 (so Windows will be reinitialized upon boot) use the following command:
shutdown /r /f /t 0
Additional information: If you want your system to perform a full shutdown every time you press the Shutdown button from Charms bar, then you have to disable the Fast Startup Option from the control panel. For detailed instructions on how to do that read this article: How to disable Fast Startup in Windows 8 and 8.1