Have you ever wondered how exactly the Windows boot process happens? What processes happen in the background when you press the power button until Windows is ready for you?
If yes, then you are in the right place. In this article, Bardimin will explain how all these processes occur. You see it all as one process when everything happens gradually. It has been designed in such a way that if you face any problem with Windows Boot, you can solve it.
The Windows boot process consists of the following steps:
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Stage 1: PreBoot
When you press the power button, the system will be turned on. Then the video will be initialized and hardware self-testing is performed. The BIOS performs these tests, called POST (Power-On Self-Tests). Usually, the memory test is the most visible on the screen and the progress of the test results is also displayed.
After running POST, the system initializes each adapter. If the adapter has its own built-in BIOS, the adapter BIOS is called to perform its initialization. For each connected drive adapter, its specifications and access method will be asked.
Some adapters, such as SCSI adapters, display messages and allow users to interact. Some adapters that do not have a BIOS are not initialized until Windows loads its drivers in the boot-up process.
Stage 2: Windows Boot Manager
After all, adapters that have BIOS are initialized, and the system boot loader reads the sector located at the very earliest part of the first bootable disk drive and forwards commands to this code. This sector is called the boot sector, or MBR (Master Boot Record), and is written by the operating system when the operating system is installed.
The code in the MBR then loads the NTLDR file. (This file has no extension, although it is an executable file.) Once loaded, the MBR passes control to code in NTLDR.
NTLDR then loads a special copy of the required file system I/O files and reads it in the boot.ini file. The boot.ini file has information about each operating system that can be loaded. Remember, Windows supports multi-boot configurations.
The boot loader can even boot two different copies of Windows with the same or different version numbers.
Stage 3: Windows OS Loader
NTLDR then processes boot.ini, displaying boot information that lets the user choose which operating system to load. At this point, let’s assume that Windows will load.
When you select Windows to load, NTLDR loads the ntdetect.com file. The program then collects information about the currently installed hardware and stores this information in the registry. Most of this information is stored in the “HKEY_LOCAL_MACHINE”.
Once NTDETECT detects the hardware, the control is returned to NTLDR, and the boot process resumes. At this point, the registry has been substantially updated with the current hardware configuration, which is stored in”HKEY_LOCAL_MACHINE\Hardware”.
Stage 4: Windows NT OS Kernel
Following NTDETECT’s detection, NTLDR loads and initializes the Windows kernel loads the service, and then starts Windows.
When the kernel is loaded, the HAL (Hardware Abstraction Layer) is also loaded. Next, the system registry subkey “HKEY_LOCAL_MACHINE\System” is loaded into memory. Windows scan the registry for all drivers with an initial value of zero. This includes drivers that must be loaded and initialized at boot time.
You can see the beginning of the next stage, kernel initialization. The screen switches to a blue background, the system scans the registry, and finds all the drivers that should be run at the kernel initialization stage.
From this point on, Windows runs various components and systems. Each component and system read the registry and performs various tasks and functions. In the last stage, the program that manages user logon, WinLogon, starts. WinLogon allows users to log on and use Windows.