A: One of the reasons Windows 8 starts so fast normally is that it doesn’t shut down the kernel session, which contains the system state and takes most of the time to start to initialize during system boot. Instead, the kernel session is actually hibernated, taking up a very small amount of disk space and making it quickly write and read again at startup.

This does mean that between boots, the system isn’t re-initialized (because it’s not typically needed). If you do make a hardware or system change that requires a system initialization, the system typically handles this for you automatically.

However, you can also force a full shutdown, and therefore full system initialization at next start, by adding the /full switch to the shutdown.exe command. For example, entering

shutdown /s /full /t 0
performs a full shutdown (not hibernating the kernel session) with no time delay.

For more information on the boot changes in Windows 8 see the MSDN blog about boot times.  It’s a great read.