Starting a System with Configuration Problems

This section describes how to start a computer when hardware or software problems prevent normal system startup.

For a Windows NT computer, the Registry includes several control sets. Each control set is a complete set of system parameters that define startup, system recovery, and driver load controls plus service parameters and other system configuration data. The control set represented as the CurrentControlSet in the Registry is a link to the control set used to start the system for the current session. For details about control sets, see "HKEY_LOCAL_MACHINE\SYSTEM Subtree" in Chapter 10, "Overview of the Windows NT Registry."

Whenever you start Windows NT, the Boot Loader automatically tries to boot using the CurrentControlSet described in the HKEY_LOCAL_MACHINE\SYSTEM\Select subkey. If the system cannot start using this control set (because of erroneous user changes or bad-sector errors on a file), the Boot Loader automatically tries the LastKnownGood control set, as defined in the Select subkey.

You can also switch to a previous system configuration manually, bypassing the automatic process.

To manually switch to a previous system configuration

1. Press Enter to select Windows NT at the startup prompt, and then immediately press the spacebar.
2. From the Configuration Recovery menu, choose the command named Use Last Known Good Configuration, and then press Enter.

Note Choosing the Last Known Good option at startup causes the system to discard all configuration changes made since the computer's last successful startup.

During system startup, you can only choose between the current and the LastKnownGood control set. For information about how the LastKnownGood control set is selected and stored, see "HKEY_LOCAL_MACHINE\SYSTEM Subtree" in Chapter 10, "Overview of the Windows NT Registry."