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If you make changes to the Windows registry manually, or if changes are made to the Windows registry during installation or uninstallation of software or a device driver, Windows 8 or Windows Server 2012 does not immediately make changes to the registry.
Such registry updates are not immediately erased from disk. Instead, the modified recording data is regularly rinsed on the hard disk at short intervals.
Now that changes have been made to the registry when you are faced with a scenario where your computer immediately shuts down due to a power failure or unexpected reason, registry changes may not be saved. In this case, the application may not work properly when you restart your PC and registry changes are not visible at all. Even newly installed drivers do NOT appear to be installed – or uninstalled drivers continue to appear as installed.
In such situations, you must modify the registry, reinstall or uninstall the software or driver.
All pending write requests, including registry changes, are stored on the hard disk before the system stops, i.e. during Shutdown, Restart, Sleep, and Hibernation options.
Note that if you set the power button to Do nothing, the pending entries will not be saved.
If you wish, you can ask Windows 8 to write registry changes immediately to disk. For this, you need the RegFlush API. However, this process is costly in terms of resources used and can affect the performance of your system.
KB2784761 say that’s how they do it to maximize Windows 8 performance.