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Window XP Startup Program the Startup ProcessWindow XP Startup Program describes the Window XP Professional startup process. Every time you turn your system on for the first time or you restart your system after installing software you just downloaded from the internet, you go through the Windows XP startup process. So it becomes important to take note of what phases the Windows XP startup process goes through. If the Windows XP startup process had an error while starting up, you need to know which phase was processing. So by understanding the different Window XP startup phases you can pinpoint what the most likely solution will be. All computers running Window XP Professional share the same Window XP startup sequence:
The preceding Window XP Startup program sequence applies to systems started or restarted after a normal shutdown. It does not apply when you bring your computer out of hibernation or standby. For Window XP Professional to start, the system and boot partitions must contain the files listed below:
Window XP Startup Program Files:
Window XP Startup Program - Phase 1 Power-On Self Test (POST) Phase As soon as you turn on the computer, its CPU - Central Processing Unit begins to carry out the programming instructions contained in the basic input/output system (BIOS). The BIOS, which is a type of firmware, contains the processor-dependent code that starts the computer regardless of the operating system installed. The first set of Window XP startup program instructions is the power-on self test (POST). The POST is responsible for the following system and diagnostic functions:
After the Motherboard POST completes, add-on adapters that have their own firmware (for example, Video Cards and Hard Drive controllers) carry out internal diagnostic tests. Window XP Startup Program - Phase 2 Initial Startup Phase After the POST, the settings that are stored in CMOS memory, such as boot order, determine the devices that the computer can use to start an operating system. For example, if the boot order specifies the floppy disk as the first Window XP startup program device and the Hard Drive as second (some firmware displays this order as "A, C"), the following scenarios might occur at startup: The floppy disk drive contains a floppy disk The BIOS searches the floppy disk drive for a bootable floppy disk. If one is present, the first Window XP startup program sector (the floppy disk boot sector) loads into RAM - Random Access Memory. If the floppy disk is not bootable, an error message similar to the following appears:
The computer displays the preceding message until you insert a bootable floppy disk or until you remove the floppy disk and restart the computer. The floppy disk drive does not contain a floppy disk If you restart the computer without a floppy disk, the computer reads the boot code instructions located on the master boot record (MBR). The MBR is the first Window XP startup program sector of data on the Window XP startup program hard disk and contains instructions (called boot code) and a table (called a partition table) that identify primary and extended partitions. The BIOS reads the MBR into memory and transfers control to the code in the MBR. The computer then searches the partition table for the active partition. The first Window XP startup program sector of the active partition contains boot code that enables the computer to do the following:
If an active partition does not exist or if boot sector information is missing or corrupt, a message similar to any of the following might appear:
If an active partition is successfully located, the code in the boot sector locates and starts Ntldr and the BIOS releases control to it. The boot order specifies another Window XP startup program device In addition to floppy disks or Hard Drive attached to SCSI and ATA controllers, some computer firmware can start an operating system from other devices, such as:
It is possible to specify a custom boot order, such as "CD-ROM Drive, A, C". When you specify "CD-ROM Drive, A, C" as a boot order, the following events occur at startup:
There are exceptions where code on bootable media transfers control to the Hard Drive. For example, when you start your system by using the bootable Window XP Professional operating system CD, Setup checks the Hard Drive for Window XP Professional installations. If one is found, you have the option of bypassing CD-ROM Window XP startup program by not responding to the Press any key to boot from CD prompt that appears. You cannot use a nonbootable CD to start your system. The presence of a nonbootable CD in the CD-ROM Drive can add to the time the system requires to start. If you do not intend to start the system from CD, remove all CDs from the CD-ROM Drive before restarting. Window XP Startup Program - Phase 3 Boot Loader Phase Ntldr loads Window XP startup program files from the boot partition and then does the following: Sets an x86-based processor to run in 32-bit flat memory mode An x86-based computer first starts in real mode. In real mode, the processor disables certain features to allow compatibility with software designed to run on 8-bit and 16-bit processors. Ntldr then switches the processor to 32-bit mode, which allows access to large amounts of memory and enables Window XP Professional to start. Starts the file system Ntldr contains the program code that Window XP Professional needs to read and write to disks formatted by using the NTFS or file allocation table (FAT16 or FAT32) file systems. Reads the Boot.ini file Ntldr parses the Boot.ini file to determine the location of the operating system boot partition. For systems that use a single-boot configuration, Ntldr initiates the hardware-detection phase by starting Ntdetect.com. For multiple-boot configurations that include Window XP Professional, Windows 2000, Windows Server 2003, Windows NT 4.0, Windows 95, Windows 98, Windows Me, or MS-DOS, you receive a menu of operating system choices at startup. In addition, if the Recovery Console has been installed, the boot loader menu is displayed during Window XP startup program with the Recovery Console as one of the available options. If you choose Window XP Professional, Windows 2000, Windows Server 2003, or Windows NT 4.0, Ntldr proceeds with the hardware-detection phase. If you do not select Window XP Professional, Windows 2000, Windows Server 2003, or Windows NT 4.0, control is passed to the boot sector for the other operating system. For example, if you select Windows 95, Windows 98, Windows Me, or MS-DOS, Ntldr passes control to Bootsect.dos by reading MBR code that Bootsect.dos contains. This action causes the MBR code in Bootsect.dos to execute as if the instructions were read from the disk. Detects hardware and hardware profiles Ntldr starts Ntdetect.com, a program that performs basic device detection. Ntldr then passes Boot.ini information, as hardware and software data in the registry, to Ntoskrnl.exe. Ntdetect.com detects hardware profile information (for example, docked and undocked configurations for portable computers). It also checks for information stored in Advanced Configuration and Power Interface (ACPI) tables. ACPI-compliant firmware enables Window XP Professional to detect device power management features and determine device resource requirements.
Window XP Startup Program - Phase 4 Detect and Configure Computer Hardware Equipment Phase After processing the Boot.ini file, Ntldr starts Ntdetect.com. Ntdetect.com collects information about installed Computer Hardware Equipment by using calls to system firmware routines. Ntdetect.com then passes this information back to Ntldr. Ntldr gathers the data received from Ntdetect.com and organizes the information into internal data structures. Ntldr then starts Ntoskrnl.exe and provides it with information obtained from Ntdetect.com. Ntdetect.com collects the following type of Computer Hardware Equipment and device information:
For computers with ACPI firmware, Window XP Professional assigns the Computer Hardware Equipment resources to use. During this phase, Ntdetect.com searches for Computer Hardware Equipment profile information. Window XP Professional assigns the Computer Hardware Equipment resources to use. During this phase, Ntdetect.com searches for Computer Hardware Equipment profile information. Window XP Professional creates a single default profile for desktop computers and creates two default profiles for portable computers. For portable computers, the operating system selects the appropriate profile based on the Computer Hardware Equipment state of the computer:
Computer Hardware Equipment profiles are especially useful for portable computers because the Computer Hardware Equipment state of these computers is not static. Drivers for devices not listed in a particular Computer Hardware Equipment profile are not loaded during Window XP startup program. Window XP Startup Program - Phase 5 Kernel Loading Phase Ntldr is responsible for loading the Windows kernel (ntoskrnl.exe) and the Computer Hardware Equipment abstraction layer (HAL) into memory. The Hal.dll file that your computer uses can vary. During installation, Window XP Professional Setup copies one of several HAL files and renames the file Hal.dll. Together, the kernel and the HAL initialize a group of software components that are called the Windows executive. The Windows executive processes the configuration information stored in registry control sets, and starts services and drivers. Control Sets Ntldr reads control set infromation from the HKEY_LOCAL_MACHINESYSTEM registry key, which is created from information in the systemrootSystem32Config System file. So that Ntldr can determine which device drivers need to be loaded during startup. Typically, several control sets exist, which the actual number depending on how often system configuration settings change. Typical registry control set subkeys are:
Ntldr uses the control set identified by the Default value unless you choose the Last Known Good Configuration from the Windows Advanced Options menu. The kernel uses the internal data structures provided by Ntldr to create the HKEY_LOCAL_MACHINEHARDWARE key, which contains the Computer Hardware Equipment data collected at system Window XP startup program. The data includes information about various Computer Hardware Equipment components and system resources allocated to each device. To monitor the kernel load process, watch the Starting up progress indicator that appears during Window XP startup program. Window XP Professional supports an extensive set of devices. New or updated drivers that are not on the Window XP Professional operating system CD are provided by Computer Hardware Equipment manufacturers. In addition, Window XP Service Pack such as Window XP Service Pack 2 provide signed drivers for Computer Hardware Equipment devices were not available when Windows XP was first released. Drivers are kernel-mode components required by devices to function within an operating system. Services are components that support operating system functions and applications. Services can run in a different context than user applications and typically do not offer many user-configurable options. Services, such as the Print Spooler, do not require a user to be logged on to run and act independently of the user who is logged on to the system. Window XP Professional driver and services files are typically stored in the systemrootSystem32 and systemrootSystem32Drivers folders and use .exe or .dll file name extensions. Drivers are also services. Therefore, during kernel initialization, Ntldr and Ntoskrnl.exe use the information stored in the HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServiceservicename registry subkeys to determine both the drivers and services to load. For example, Ntldr searches the Services subkey for drivers with a Start value of 0, such as hard disk controllers. After Ntldr starts Ntoskrnl.exe, an Ntoskrnl.exe component searches for and starts drivers, such as network protocols, that have a Start value of 1. The table below lists the values (in decimal) for the Start entry. Boot drivers (those with a Start value of 0) and file system drivers are always loaded regardless of their Start value because they are required to start Window XP Professional.
Values for a (servicename) Start Entry
Values for a (servicename) Type Entry
Some drivers and services require that certain dependencies be met before they start. You can find dependencies listed under the DependOnGroup and DependOnService entries in the HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesservicename subkey for each service or driver. The Services subkey also contains information that affects how drivers and services are loaded, a few of which are in table below.
Other Registry (servicename) Entries
Session Manager After all entries that have Boot and Startup data types are processed, the kernel starts Session Manager. Session Manager (Smss.exe) performs important initialization functions, such as:
The Windows subsystem and the applications that run within it are user mode processes; they do not have direct access to Computer Hardware Equipment or device drivers. User-mode processes run at a lower priority than kernel-mode processes. When the operating system needs more memory, it can page to disk the memory that is used by user-mode processes. Session Manager searches the registry for service information. Window XP Startup Program - Phase 6 Logon Phase The Windows subsystem starts Winlogon.exe, a system service that enables logging on and off. Winlogon.exe then does the following:
The Graphical Identification and Authentication (GINA) component collects the user name and password, and passes this information securely to the LSA for authentication. If the user supplied valid credentials, access is granted by using either the Kerberos V 5 authentication protocol or NTLM. Winlogon initializes security and authentication components while the Service Control Manager initializes Auto-load services and drivers. After the user logs on, the following events occur:
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