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 computer running Windows NT, 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 that appears under the CurrentControlSet key is the one used to start the system for the current session. For details about control sets, see "HKEY_LOCAL_MACHINE\System Key" in Chapter 23, "Overview of the Windows NT Registry."

Whenever you start Windows NT, the Boot Loader automatically tries to boot by using the current control set described under the HKEY_LOCAL_MACHINE\System\Select subkey. If the system cannot start by 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 the Last Known Good 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 Hardware Profile\Configuration Recovery menu, click Use Last Known Good Configuration, press L, then press enter.

Note

If you select the LastKnownGood option at startup, the system discards any configuration changes to the HKEY_LOCAL_MACHINE\System\CurrentControlSet subkey made since the computer's last successful startup.

During system startup, you can choose between the default and the LastKnownGood control set only. For information about how the LastKnownGood control set is selected and stored, see "HKEY_LOCAL_MACHINE\System Key" in Chapter 23, "Overview of the Windows NT Registry."

If you have created more than one hardware profile, you can also choose a hardware profile. A hardware profile is a set of changes to the standard configuration of services (including drivers and Win32 services) and devices loaded when Windows NT starts.

For more information on hardware profiles, double-click System in Control Panel, click the Hardware Profiles tab and open Help. See also "Hardware Profiles Subkey for All Control Sets" in Chapter 23, "Overview of the Windows NT Registry."