Boot Sequence of Windows XP and Later

Hi all geeks,

Here's the most common encountered computer process we all know but seldom know how it goes really. Not too techie... now we are going to see the booting sequence of an OS. (Windows XP and Later)

Diagnosing and correcting hardware and software problems that affect the startup process is an important troubleshooting skill. Resolving start up issues requires a clear understanding of the startup process and core operating system components.

The sequences occur during the Windows XP Professional boot process are:

Pre-boot sequence
Boot sequence
Kernel load sequence
Kernel initiation sequence
Logon sequence

The boot sequence is as follows

Pre-boot sequence:

1. Power on self test (POST) routines are run
2. Master Boot Record is loaded into memory, and the program is run

Boot sequence:

1. The Boot Sector from Active Partition is Loaded into Memory
2. Ntldr is loaded and initialized from the boot sector
3. Change the processor from real mode to 32-bit flat memory mode
4. Ntldr starts the appropriate mini file system drivers. Mini file system drivers are built into Ntldr and can read FAT or NTFS
5. Ntldr reads the Boot.ini file
6. Ntldr loads the operating system selected, on of two things happen
   * If Windows NT is selected, Ntldr runs Ntdetect.com
   * For other operating system, Ntldr loads and runs Bootsect.dos and passes control to it. The Windows NT process ends here

Kernel load sequence:

1. Ntdetect.com scans the computer hardware and sends the list to Ntldr for inclusion in HKEY_LOCAL_MACHINE\HARDWARE

Kernel initiation sequence:

1. Ntldr then loads Ntoskrnl.exe, Hal.dll and the system hive
2. Ntldr scans the System hive and loads the device drivers configured to start at boot time

Logon sequence:

1. Ntldr passes control to Ntoskrnl.exe, at which point the boot process ends and the load phases begin

 Note:

• Ntldr is responsible for loading the operating system.
• MBR – Master Boot Record.