LastKnownGood

Last Known Good Configuration is a startup recovery option in Windows NT–based operating systems that allows the system to boot using the registry and driver configuration from the last successful startup. It is designed to help recover from problems caused by faulty driver updates or incorrect system settings that prevent Windows from starting correctly. It does not recover personal files and is not a full backup or system restore.

When selected, Windows loads the registry configuration from the last successful boot and bypasses recently installed drivers and services that could have caused the failure. This can restore a usable boot environment in many cases, but it does not fix underlying data corruption, hardware problems, or issues that existed before the last good boot. A subsequent normal reboot can reintroduce changes if the underlying cause is not resolved.

Usage and availability: The option is typically accessed via the Advanced Boot Options menu, often by pressing F8 during startup, and selecting Last Known Good Configuration. In some editions or newer Windows releases, the option may be absent, with recovery tasks provided by System Restore, Startup Repair, or Safe Mode instead. It is considered a short-term recovery tool rather than a comprehensive backup or long-term solution.

History: The feature has been part of the Windows NT family since older versions and gained prominence in Windows 2000 and Windows XP as a way to recover from registry corruption caused by faulty updates or misconfigurations. In modern Windows editions, emphasis has shifted toward System Restore and startup repair utilities, and Last Known Good Configuration is less commonly used. See also System Restore, Safe Mode, and Startup Repair.