The Basic Concept – Windows Boot Process


The Windows Boot Process

There are five major sequences that occur during the Windows boot process.

The Windows boot process

Figure: The Windows boot process.

The sequences are described in the following table.

Pre-boot sequence :

The pre-boot sequence begins when the power is turned on. The computer runs Power-On Self Test (POST) routines to determine the amount of physical memory and to identify and check the other hardware components present. If the computer has a PnP BIOS, the hardware is recognized and configured. The computer’s BIOS locates the boot device, and then loads and runs the Master Boot Record (MBR).

Boot sequence :

The boot sequence is when the operating system is selected, and the hardware con- figuration is detected and loaded. It has four subphases: initial boot loader, operating system selection, hardware detection, and configuration selection. In Windows 7, this is accomplished by the winload.exe and Windows Boot Manager components. In Windows XP and earlier operating systems that use the NT kernel, this was done with NTLDR (NT Loader) and the boot.ini file.

Kernel load sequence :

During the kernel load sequence, the operating system components are loaded into memory.

Kernel initiation sequence :

In the kernel initiation sequence, the Windows kernel takes control of the system. At this point, the Microsoft Windows logo appears, along with a status bar.

Logon sequence :

During the logon sequence, Winlogon.exe starts the Local Security Authority (LSA), and the Logon screen or Logon dialog box appears. Users can now log on, while Windows continues to load low-level drivers and services in the background. The boot process is considered complete when a user successfully logs on. The Clone control set built is copied to a new control set called LastKnownGood, thus preserving a copy of the settings in the successful boot sequence.

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