Using the last known good configuration

Many errors occur due to a configuration change. For example, you might install a new device driver and find that the system suddenly doesn’t boot because of it. A new application can cause the system to fail as well. Any change that affects the boot sequence can cause problems that seem impossible to fix. The Last Known Good Configuration (Advanced) option lets you use the configuration from the last time that Windows booted successfully without using any of the special options. Think of it as an undo feature — you can reverse the effects of a single bad decision, configuration change, or installation.

Of course, this feature isn’t the same as creating a system restore point. You can use it only to reverse changes that prevent the system from booting properly. A system restore point is an automatic or manual process of saving the system settings when a major system change occurs or simply because you want to save your system setup (always a good idea when you install a new application). Never count on the Last Known Good Configuration (Advanced) option as a replacement for creating a system restore point.

You can’t undo the use of the Last Known Good Configuration (Advanced) option. Any changes that you reverse using this feature are gone, which makes this option a hammer when you really wanted a screwdriver. Always use this option with care. It’s really a last-ditch effort to get your server going again when all other options have failed.

Source of Information : For Dummies Windows Server 2008 All In One Desk Reference For Dummies