Boot Loader is the part of the OS that enables booting process and loading the particular OS while start up.

The function of the Boot Loader is to perform and start up options while the users turn on the system.

The Boot Loader includes some files that are responsible for enabling the boot processes.

While you booting the computer, the NTLDR file from the Windows XP takes the charge and start up the Proper OS.

The BOOT.INI file will help NTLDR to find the location of the OS.

The Boot Loader also performs the options for Recovery Console and Safe Mode computing along with the OS.

In the case of Dual Booting, Boot Loader is responsible for changing the Partition Settings.

PROCESS:-

1. First is the POST(Power On Self Test) this process tests memory as well as other subsystems.

2. Once the POST is completed the BIOS comes sure that everything is working properly.

The BIOS will then attempt to read the MBR (Master Boot Record) this is the first sector of the first hard Drive.

3. MBR looks the Boot Sector of the active partition, that is where NTLDR is located. NTLDR is the Boot Loader for Windows XP.

NTLDR will allow memory addressing, initiate the file system, read the Boot.INI and load the Boot menu.

NTLDR has to be in the root of the Active Partition as NTDETECT.COM, BOOT.INI, BOOTSECT.DOS (for Multi OS), NTBOOTDD.SYS (SCSI adapters).

4. Once XP is selected from Boot menu, NTLDR will run NTDETECT.COM, BOOT.INI, BOOTSECT.DOS to get proper OS selected and loaded.

5. NTLDR will then load NTOSKRNL.EXE and HAL.DLL these two files are in Windows XP located in %SYSTEMROOT%SYSTEM32

6. NTLDR reads the registry chooses a Hardware profile and authorizes Device Drivers in the exact order.

7. At this point NTOSKRNL.EXE takes over. It starts WINLOGON.EXE that in turn starts LSASS.EXE this is the program that display the logon screen so that you can logon.