Section 3.4: Identifying Boot Sequences
As mentioned earlier, there are two forms of booting - the soft boot and the hard boot.
The hard boot occurs when you power on your computer with an initial zero power supply and a warm boot occurs when your computer reboot takes place as a part of installation of software. While you boot your computer, your computer goes through a detailed set of procedures and performs all system checks and loads all necessary files to bring the computer to an operable state.
The Windows XP Professional startup process closely resembles the start up process of Microsoft Windows NT 4/2000/2003, but it different from Microsoft MS-DOS, Windows 95/98/Me.
The startup sequence of Windows XP is:
- Power-on self test (POST) phase: At this stage, a self-test is performed by the power supply to ensure that the power signals are sent to the processor and the hardware. It also checks that the devices needed are present and store the settings in CMOS memory.
- Initial startup phase: At this stage, the system determines the devices that the computer can use to start an operating system. It determines the boot sequence of devices on the basis of BIOS settings.
- Boot loader phase: At this stage, the control is passed to the partition loader code that accesses the partition table and identifies the primary partition, extended partitions, and active partitions. The operating system loader file - NTLDR is detected and loaded. This file in turn loads the Boot.ini file to determine the location of the operating system boot partition. The boot up menu is displayed if you have more than 2 operating systems installed in your computer.
- Detect and configure hardware phase: At this stage, NTLDR starts Ntdetect.com and performs basic device detection. It searches for hardware profiles information and loads the essential software drivers to control the hardware devices. It then passes all information from the Windows registry and Boot.ini file into Ntoskrnl.exe.
- Kernel loading phase: Ntoskrnl loads the XP kernel, hardware abstraction layer and registry information.
- Logon phase: The Ntoskrnl.exe starts Winlogon.exe that enables logging on and off.
In Windows Vista the bootstrap process is slightly different from XP. Windows Vista no longer looks for Ntldr rather it looks for a new boot loader called Bootmgr, which loads the Boot Configuration Database (BCD). The BCD then loads an OS loader boot application Winload.exe that initializing the kernel.
The boot configuration stored by Boot.ini in previous Windows versions is now stored in an extensible database, BootBCD, the Boot Configuration Database (BCD).
Section 3.4.1: The Advanced Boot Options
In case of problems, Windows offers a number of advanced startup options and utilities to repair your system. The advanced startup options can be seen by pressing F8 key before the Windows start. The advanced startup options are:
- Safe mode: This option loads Windows with a minimal set of drivers. This option is best to perform any kind of troubleshooting.
- Safe mode with networking: This option loads Windows in safe mode with a minimal set of drivers but also includes the network drivers and services that are needed to access the Internet or other computers on the network
- Safe mode with command prompt: This option loads Windows in safe mode with a command prompt window.
- Enable boot logging: This option creates a text file called ntbtlog.txt which is a log file that has the log entries of all the drivers that are installed during startup.
- Enable low resolution video (640 x 480): This option loads Windows with low resolution and refresh rate settings.
- Last Known Good Configuration (advanced): This option loads Windows with the last registry and driver configuration that worked successfully.
Section 3.4.2: Recovery Options
The recovery options provided by Windows allow you to recover your Windows OS if the system fails and you are unable to boot Windows. The following recover options are available:
- Recovery Console: The Recovery Console is available in Windows XP/2000/2003 and is not available in Windows Vista. It is a command line utility that allows you to repair or replace important operating system files, format drives, and stop and start Windows services. It can be installed through Windows installation CD or can be accessed from the boot menu if it has already been installed on your system.
A number of commands are available in Recovery Console. Some of these commands include Attrib, Batch, Bootcfg, Chkdsk, Diskpart, Fixboot, and fixmbr commands to change the attributes of a single file or a directory, run a series of other Recovery Console commands, build or modify the boot.ini file, correct hard drive errors, create or delete partitions on hard drives, write a new partition boot sector to the system partition, and write a new master boot record to the hard disk drive respectively.
- Emergency Repair Disk (ERD): The ERD is available in Windows 2000 only. The Windows Backup and Restore utility provides you an option to create an ERD that allows you to repair files or even perform a full recovery by restoring from your last system backup if necessary in case a failure occurs. The ERD should be recreated after each service pack, system date, or updated driver is installed.
- Automatic System Recovery (ASR): The ASR is available in Windows XP only. It allows you to restore the entire system that includes the Windows files, and Registry settings. It does not restore data files. To restore data files, you need to back up the data files separately on a regular basis.
- Restore Points: The Restore points are available in Windows XP and Windows Vista. It is the most powerful tool and is enabled by default. It keeps creating the entire backup of the system and allows you to restore back your system at a previous date. If required you can also configure Restore points manually. You can access this by clicking Start->All Programs->Accessories->System Tools->System Restore.