Troubleshooting Startup ProblemsLesson 6

Objectives

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Windows Boot Process• If the system is running Windows 7, the

system will go through the following steps:1. BOOTMGR is loaded and accesses the

Boot Configuration Data Store to display the boot menu or to boot from a partition or volume.

2. WINLoad is the operating system boot loader that loads the rest of the operating system.

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Windows Boot Process

3. NTOSKERNL.EXE is the main part of Windows, which is responsible for various system services, processes, and memory management.

4. Boot-class device drivers implement a number of functions that are utilized in different ways by different hardware platforms based on processor and chipset.

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Master Boot Record• A master boot record (MBR) is the first

512-byte boot sector of a partitioned data storage device such as a hard disk.

• It contains the disk’s primary partition table, and the code to bootstrap an operating system, which usually passes control to the volume boot record and uniquely identifies the disk media.

• By default, the master boot record contains the primary partition entries in its partition table.

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Volume Boot Record• A volume boot record (VBR), also

known as a volume boot sector or a partition boot sector, is a type of boot sector, stored in a disk volume on a hard disk, floppy disk, or similar data storage device that contains code for booting an operating system such as BOOTMGR.

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System and Boot Partition/Volume• The active partition is the partition or

volume that is marked as the partition to boot from. The active partition or volume that contains the boot file (BOOTMGR) is known as the system partition/volume.

• The partition or volume that contains the Windows operating system files (usually the Windows folder) is called the boot partition.

• It is common for computer systems to have one drive and one partition/volume, which makes the partition both the system partition and the boot partition.

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%SystemRoot% Variable• The %SystemRoot% variable is a

special system-wide environment variable found on Microsoft Windows systems. Its value is the location of the system folder, including the drive and path. By default, on a clean installation of Windows 7, the Windows files are placed in the C:\Windows folder.

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Boot Configuration Data (BCD)• Boot Configuration Data (BCD) is

a firmware-independent database for boot-time configuration data used by Microsoft’s Windows Boot Manager found with Windows Vista, Windows 7, and Windows Server 2008.

• To edit the Boot Configuration, you would typically use Bcdedit.exe.

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Bcdedit Command• The Bcdedit.exe command-line tool

can be used to add, delete, and edit entries in the BCD store, which contains objects. Each object is identified by a GUID (Globally Unique Identifier).

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Bcdedit Command

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Advanced Boot Menu• When you have some problems that

occur during boot up, you may need to take some extra steps to get the computer in a usable state so that you can fix the problem.

• Since Windows XP, you can use the Advanced Boot Menu to access advanced troubleshooting modes.

• To access the Advanced Boot Options screen, turn your computer on and press F8 before the Windows logo appears.

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Advanced Boot Menu

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Advanced Boot Menu• Repair Your Computer: Shows a

list of system recovery tools you can use to repair startup problems, run diagnostics, or restore your system. This option is available only if the tools are installed on your computer’s hard disk.

• Safe Mode: Starts Windows with a minimal set of drivers and services. If you make a change to the system and Windows no longer boots, you can try safe mode.

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Safe Mode

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Advanced Boot Menu• Safe Mode with Networking: Starts

Windows in safe mode and includes the network drivers and services needed to access the Internet or other computers on your network.

• Safe Mode with Command Prompt: Starts Windows in safe mode with a command prompt window instead of the usual Windows interface.

• Enable Boot Logging: Creates a file, ntbtlog.txt, that lists all the drivers that are installed during startup and that might be useful for advanced troubleshooting.

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Advanced Boot Menu• Enable low-resolution video

(640×480): Starts Windows using your current video driver and using low resolution and refresh rate settings. You can use this mode to reset your display settings.

• Last Known Good Configuration (advanced): Starts Windows with the last registry and driver configuration that worked successfully, usually marked at the last successful login.

• Directory Services Restore Mode: Starts Windows domain controller running Active Directory so that the directory service can be restored.

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Advanced Boot Menu• Debugging Mode: Starts Windows in an

advanced troubleshooting mode intended for IT professionals and system administrators.

• Disable automatic restart on system failure: Prevents Windows from automatically restarting if an error causes Windows to fail. Choose this option only if Windows is stuck in a loop where Windows fails, attempts to restart, and fails again repeatedly.

• Disable Driver Signature Enforcement: Allows drivers containing improper signatures to be loaded.

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System Configuration•  System Configuration (msconfig.exe) is

a tool that can help isolate problem startup programs or services that prevent Windows from starting correctly.

• When a problem occurs and assuming you can successfully start and log in to Windows, you can open System Configuration and disable certain startup programs or services.

• If the problem goes away when you restart Windows, you know that the problem is caused by the program or service that you disabled.

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System Configuration

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Windows PE• Windows Preinstallation Environment

(Windows PE) 3.0 is a minimal Win32 operating system with limited services, built on the Windows 7 kernel.

• It is used to prepare a computer for Windows installation, to copy disk images from a network file server, and to initiate Windows Setup.

• Besides being used to deploy operating systems, it is an integral component in recovery technology with Windows Recovery Environment (Windows RE).

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Windows Recovery Environment• Windows Recovery Environment

(WinRE) is a set of tools included in the Windows Vista, Windows 7, and Windows Server 2008 operating systems to help diagnose and recover from serious errors, which may be preventing Windows from booting successfully.

• WinRE may be installed and/or booted from many media including hard disks, optical media (such as an operating system installation disc), and PXE (e.g., Windows Deployment Services). 22

System Recovery Options

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BootRec Command• If you prefer to perform a manual

repair, you can use the BootRec command, which can repair the MBR or the volume boot sector.

• BootRec.exe can be executed from the Command Prompt in the System Recovery tools.

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Skill Summary• The computer goes through the power-on

self-test (POST), which initializes hardware and finds an operating system to load. – The system will search for a boot device

(such as a hard drive, optical disk, or USB flash drive) to boot from.

• If the system is running Windows 7, the system will load the BOOTMGR, WINLoad, and NTOSKERNL.EXE.

• BOOTMGR is loaded and accesses the Boot Configuration Data Store to display the boot menu or to boot from a partition or volume.25

Skill Summary• WINLoad is the operating system

boot loader that loads the rest of the operating system.

• NTOSKERNL.EXE is the main part of Windows that is responsible for various system services, processes, and memory management.

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Skill Summary• A master boot record (MBR) is the

first 512-byte boot sector of a partitioned data storage device such as a hard disk. It is used to hold the disk’s primary partition table and contains the code to bootstrap an operating system, which usually passes control to the volume boot record and uniquely identifies the disk media.

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Skill Summary• A volume boot record (VBR), also

known as a volume boot sector or a partition boot sector, is a type of boot sector, stored in a disk volume on a hard disk, floppy disk, or similar data storage device that contains code for booting an operating system such as BOOTMGR.

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Skill Summary• The active partition is the partition or volume

that is marked as the partition to boot from. The active partition or volume that contains the boot file (BOOTMGR) is known as the system partition/volume.

• The partition or volume that contains the Windows operating system files (usually the Windows folder) is called the boot partition.

• Boot Configuration Data (BCD) is a firmware-independent database for boot-time configuration data used by Microsoft’s Windows Boot Manager found with Windows Vista, Windows 7, and Windows Server 2008.

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Skill Summary• To edit the Boot Configuration, you

typically use Bcdedit.exe.• To access the Advanced Boot Options

screen, turn your computer on and press F8 before the Windows logo appears.

• Last Known Good Configuration starts Windows with the last registry and driver configuration that worked successfully, usually marked at the last successful login.

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Skill Summary• Safe mode is useful for troubleshooting

problems with programs and drivers that might not start correctly or that might prevent Windows from starting correctly.

• System Configuration (msconfig.exe) is a tool that can help identify problems that might prevent Windows from starting correctly.

• Windows Preinstallation Environment (Windows PE) 3.0 is a minimal Win32 operating system with limited services, built on the Windows 7 kernel.

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Skill Summary• Windows Recovery Environment (WinRE) is

a set of tools included in the Windows Vista, Windows 7, and Windows Server 2008 operating systems to help diagnose and recover from serious errors that may be preventing Windows from booting successfully.

• The Startup Repair tool, which is part of the System Recovery tools is capable of fixing almost any startup problem related to boot sectors, MBRs, or the BCD registry file. 32

Skill Summary• To perform a manual repair, use the

BootRec command to fix the MBR or the volume boot sector.

• You should always keep in mind that while these repairs can come in handy and save you a lot of time and effort, they do not replace a good backup.

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