How to Restore the Last Known Good Configuration

Last Known Good Configuration is usually used to enable the operating system to start if it fails after the Starting Windows logo is displayed. Using Last Known Good Configuration helps to correct instability or startup problems by reversing the most recent system, driver, and registry changes within a hardware profile. When you use this feature, you lose all configuration changes that were made since you last successfully started your computer.

Using the Last Known Good Configuration restores previous drivers and also restores registry settings for the subkey HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet. Windows Vista does not update the LastKnownGood control set until you successfully start the operating system in normal mode and log on.

When you are troubleshooting, it is recommended that you use Last Known Good Configuration before you try other startup options, such as safe mode. However, if you decide to use safe mode first, logging on to the computer in safe mode does not update the LastKnownGood control set. Therefore, Last Known Good Configuration remains an option if you cannot resolve your problem by using safe mode.

To access the Last Known Good Configuration startup option, follow these steps:

1. Remove all floppy disks, CDs, DVDs, and other bootable media from your computer and then restart your computer.
2. Press F8 at the operating system menu. If the operating system menu does not appear, press F8 repeatedly after the firmware POST process completes but before the Starting Windows logo appears. The Advanced Boot Options menu appears.
3. On the Advanced Boot Options menu, select Last Known Good Configuration (Advanced).

Use Last Known Good Configuration to restore some settings to their state during the last time a user successfully logged on.

When Windows starts, it reads status information from the file %WinDir%\Bootstat.dat. If Windows detects that the last startup attempt was unsuccessful, it automatically displays the startup recovery menu, which provides startup options similar to the Advanced Boot Options menu, without requiring you to press F8.

Note If you suspect that changes made since you last successfully restarted the computer are causing problems, do not start Windows and log on normally-logging on overwrites the LastKnownGood control set. Instead, restart the computer and use the Last Known Good Configuration. You can also log on in safe mode without overwriting the Last Known Good Configuration. For more information about control sets, see the section titled "Kernel Loading Phase" earlier in this tutorial.

How to Use System Restore

If Last Known Good Configuration fails to resolve the problem, you can manually perform a system restore if Startup Repair did not initiate it. However, Startup Repair would typically have taken this step already if it might have solved the problem. For information on how to use System Restore, see the section titled "How to Use System Restore" earlier in this tutorial.