Booting Using the Last Known Good Configuration
Each time Windows XP starts successfully in Normal mode, the system makes a note of which control set—the system’s drivers and hardware configuration—was used. Specifically, it enters a value in the following Registry key:
HKLM\SYSTEM\Select\LastKnownGood
For example, if this value is 1, it means that control set 1 was used to start Windows XP successfully:
HKLM\SYSTEM\ControlSet001
If you make driver or
hardware changes and then find that the system won’t start, you can tell
Windows XP to load using the control set that worked the last time.
(That is, the control set that doesn’t include your most recent hardware
changes.) This is called the last known good configuration,
and the theory is that by using the previous working configuration,
your system should start because it’s bypassing the changes that caused
the problem. Here’s how to start Windows XP using the last known good
configuration:
1. | Restart your computer.
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2. | When
the OS Choices menu appears, press F8 to display the Advanced Options
menu. (If your system doesn’t display the OS Choices menu, press F8
immediately after your system finishes the Power-On Self Test, which is
usually indicated by a single beep.)
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3. | Select the Last Known Good Configuration option.
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Recovering Using System Restore
The Last Known Good
Configuration option is most useful when your computer won’t start and
you suspect that a hardware change is causing the problem. You might
think that you can also use the last known good configuration if Windows
XP starts but is unstable, and you suspect a hardware change is causing
the glitch. Unfortunately, that won’t work because when you start
Windows XP successfully in normal mode, the hardware change is added to
the last known good configuration. To revert the system to a previous
configuration when you can start Windows XP successfully, you need to
use the System Restore feature.
To revert your system to a restore point, follow these steps:
1. | Select Start, All Programs, Accessories, System Tools, System Restore.
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2. | Make
sure that the Restore My Computer to an Earlier Time option is
activated and click Next. The Select a Restore Point window appears, as
shown in Figure 1.
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3. | Use
the calendar to click the date on which the restore point was made.
System Restore displays that day’s restore points in a box to the right
of the calendar.
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4. | Click the restore point you want to restore. Here are some common restore points you might come across:
| Restore Operation | A restore point set prior to a previous use of System Restore to revert the system to an earlier state | | System Checkpoint | A restore point that Windows XP creates automatically each day | | Software Distribution Service 2.0 | A restore point set prior to installing a Windows XP update | | Unsigned Driver Install | A restore point set prior to installing an unsigned device driver |
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5. | Click
Next. System Restore asks you to close all open programs and warns you
not to do anything with your computer until the restore is done.
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6. | Click
Next. System Restore begins reverting to the restore point. When it’s
done, it restarts your computer and displays the Restoration Complete
window.
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7. | Click OK.
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Tip
System
Restore is available in safe mode. So, if Windows XP won’t start
properly, and if using the last known good configuration doesn’t work,
perform a safe mode startup and run System Restore from there.
Recovering Using the Recovery Console
If Windows XP won’t
start normally, your first troubleshooting step is almost always to
start the system in safe mode. When you make it to Windows XP, you can
investigate the problem and make the necessary changes (such as
disabling or rolling back a device driver). But what if your system
won’t even start in Safe mode?
Your next step should be
booting with the last known good configuration. And if that doesn’t
work either? Don’t worry, there’s still hope in the form of the Recovery
Console, a command-line tool that enables you to launch recovery tools,
stop and start services, access files, and replace corrupted system
files. Here’s how to use it:
1. | Insert the Windows XP Professional CD-ROM.
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2. | Restart your computer. If your system prompts you to boot from the CD, press the required key or key combination.
Tip
If your system won’t
boot from the Windows XP CD, you need to adjust the system’s BIOS
settings to allow this. Restart the computer and look for a startup
message that prompts you to press a key or key combination to modify the
BIOS settings (which might be called Setup
or something similar). Find the boot options and either enable a
CD-based boot or make sure that the option to boot from the CD comes
before the option to boot from the hard disk.
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3. | When
the Welcome to Setup screen appears, press R to choose the To Repair a
Windows XP Installation Using Recovery Console option. The Recovery
Console displays a list of the Windows installations on your computer.
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4. | Type
the number that corresponds to your main Windows XP installation and
press Enter. Recovery Console prompts you to enter the Administrator
password.
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5. | Type the password and press Enter. The Recovery Console command-line prompt appears.
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The Recovery Console is
similar to the Windows XP command prompt, but it offers only limited
access to the files and folders: the %SystemRoot% folder; the root folder of any partition; and the contents of any floppy disk, CD-ROM, or other removable disk.
Here are some troubleshooting notes to bear in mind when working at the Recovery Console:
You have a large but limited set of commands at your disposal. To see a list of those commands, type help and press Enter.
If Windows XP won’t start because the BOOT.INI file is corrupted or improperly configured, you can repair it by running the BOOTCFG /REBUILD command.
To repair bad sectors on the hard disk, run the CHKDSK command. Note, however, that CHKDSK has only two switches when you run it from the Recovery Console: /P and /R. In most cases, you’ll use /R (which implies /P) to repair any bad sectors. I should point out that the /P switch is available only in the Recovery Console; you can’t use /P in the command-line version of CHKDSK.
If Windows XP won’t start because a system file is corrupted, use the COPY command to copy the file from the Windows XP CD’s I386 folder to the appropriate folder in the %SystemDrive%. This works for both regular and compressed files. If the file exists with a compressed cabinet (.cab) file, use the EXPAND command instead.
If
another operating system has taken over the partition boot sector, or
if you suspect the partition boot sector is corrupt, you can fix the
problem by running the FIXBOOT command.
If you suspect that your computer won’t start because the Master Boot Record is corrupted, you can repair it by running the FIXMBR command.
You can display a list of all the available device drivers and services by running the LISTSVC
command. If a driver or service is preventing Windows XP from starting,
you can work around this by disabling the driver or service. You do
this by running the DISABLE
servicename command, where servicename is the name of the driver or service. Run ENABLE
servicename to enable the driver or service.
When you’re finished working with the Recovery Console, type exit and press Enter.
If you run the SET
command in the Recovery Console, you’ll see a list of four environment
variables that control your ability to access and copy data while in the
Recovery Console:
| AllowWildCards | This variable determines whether you can use the ? and * wild card characters in Recovery Console commands. |
| AllowAllPaths | This variable determines whether you can use the CD command to change to any folder on the hard disk. |
| AllowRemovableMedia | This variable determines whether you can copy files from the hard disk to a removable disk. |
| NoCopyPrompt | This variable determines whether the Recovery Console warns you when the COPY command will overwrite an existing file. |
| | Each variable is set to FALSE, by default. Unfortunately, if you attempt to use SET to change the value of any variable, Recovery Console tells you that the SET
command is disabled. To enable this command, you need to adjust a group
policy setting. (Of course, if you can’t start Windows XP, this won’t
do you much good now. However, I’m letting you know about it just in
case you need it for future troubleshooting missions.) In the Group
Policy editor, open the Computer Configuration, Windows Settings,
Security Settings, Local Policies, Security Options branch. Enable the
Recovery Console: Allow Floppy Copy and Access to All Drives and All
Folders policy. |
| | Note,
too, that you can also enable the Recovery Console: Allow Automatic
Administrative Logon policy. Doing this prevents you from being prompted
for a password when you start the Recovery Console. This is quite
dangerous, of course, so enable this policy only if you’re sure that no
one else has access to your computer. |
Reinstalling Windows XP
If
you can’t get Windows XP back on its feet using the Recovery Console,
you might be able to fix things by reinstalling Windows XP over the
existing installation. This won’t affect your data or any personal
settings you’ve adjusted, but it might cure what’s ailing Windows XP
either by restoring the system to its default settings or by installing
fresh copies of corrupted system files. Here are the steps to follow to
reinstall Windows XP:
1. | Insert the Windows XP Professional CD-ROM.
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2. | Restart your computer. If your system prompts you to boot from the CD, press the required key or key combination.
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3. | When the Welcome to Setup screen appears, press Enter to choose the To Set Up Windows XP Now option.
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4. | When
the Licensing Agreement appears, press F8 to accept it. Setup then
displays a list of Windows XP installations on your computer.
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5. | If you have more one Windows XP installation, select the one you want to fix.
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6. | Press R to choose the To Repair the Selected Windows XP Installation option.
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Recovering Using Automated System Recovery
If
nothing can get Windows XP up and running again, you have no choice but
to start with a clean slate. This means either formatting the %SystemDrive%
partition or, if hard disk errors are the culprit, replacing your hard
disk. This will be less catastrophic if you followed my advice and used
the Automated System Recovery Preparation Wizard to make backups of your
system files. If so, here are the steps to follow to recover your system:
1. | Insert the Windows XP Professional CD-ROM.
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2. | Restart
your computer. If your system prompts you to boot from the CD, press
the required key or key combination. Watch the bottom of the screen for
the following prompt:
Press F2 to run Automated System Recovery (ASR)...
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3. | Press F2. Setup asks you to insert the ASR disk.
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4. | Insert
the disk and then press any key. Setup continues the Windows XP
installation. Note that, along the way, Setup automatically formats the %SystemDrive% partition.
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From
here, the Setup program proceeds normally, except that it uses the
information on the ASR disk to restore your system files and settings
from the backup you made using the ASR Preparation Wizard. If you also
backed up your application and data files, use the Backup utility to
restore them now.
