Windows XP Boot Sequence

The Windows XP Boot Process – in detail:

Files Needed: NTLDR, NTDETECT.COM, BOOT.INI, NTOSKRNL.EXE, BOOTSECT.DOS, NTB00TDD.SYS, HAL.DLL, WINLOGON.EXE, LSASS.EXE

BOOT.INI: Provides information about the location of the Operating System. If more than one Operatig system is installed in the computer, it is displayed during the boot process.

NTLDR: Is the Windows Boot- Strap Loader (Which means it is a special application that is responsible to start up other files or programs which are needed to boot up Windows.)

NTDETECT.COM: transfers information about the computers Hardware to NTLDR.

BOOTSECT.DOS is required during Dual Boot situations only.

NTBOOTDD.SYS is required when SCSI or ATA devices like Hard-disk Drives need to be accessed.

HAL.DLL is the Hardware Abstraction Layer DLL file. The Windows XP disk contains many DLL files. Windows copies all the Dll files required for your computer and names them as HAL.DLL.
The Windows XP Boot Process – Explained:

The first step in the Windows XP Boot Process is the POST (Power On Self Test) – All the important Hardware Components are checked during this process. (Do you remember seeing the Memory getting checked at startup?) At this stage, if any of your add-on cards have a seperate BIOS (example: your Video Card), that will also be checked.

Once the POST is done, your computer will look for the Bootable device as specified in the BIOS and will load the MBR into Memory.

The BIOS then looks for and transfers control to a code in the MBR (Master Boot Record) – Windows XP takes over from here. This code starts up NTLDR.

NTLDR then activates NTDETECT.COM which then reads the BOOT.INI file. Boot.ini contains information about the location of the Operating System.

The next file to be loaded is HAL.DLL, which passes control to the Windows XP Kernel by starting NTOSKRNL.EXE.

NTOSKRNL.EXE is responsible to identify, load and activate all the device drivers in the computer. All device drives and Windows services will be available after this point. NTOSKRNL then activates WINLOGON.EXE. This file (Winlogon.Exe) starts LSASS.EXE which shows up the Windows Logon Screen.

When you enter your Username and Password, your settings get loaded.