Windows 10 Booting process in details

Hi TuhinSinharoy!

I'm Donny and I'm a Windows 10 expert. I'd love to help you out with your question.

First off, Windows 10 boot process on BIOS systems comprises of four major phases. It starts from POST and ends up in loading the Windows OS Loader or the Kernel. Here is the list of stages it goes through:

1. PreBoot
2. Windows Boot Manager
3. Windows OS Loader
4. Windows NT OS Kernel

During every process, a program is loaded. Depending on whether it uses Legacy BIOS or UEFI, the file paths and files change.

1.) PreBoot: POST or Power-On Self-Test loads firmware settings. It checks for a valid disk system, and if the system is good to go for the next phase. If the computer has a valid MBR, i.e. Master Boot Record, the boot process moves further and loads Windows Boot Manager.

2.) Windows Boot Manager: This step determines if you have multiple OS installed on your computer. If yes, then it offers a menu with the names of the OSs. When you select the OS, it will load the right program, i.e. Winload.exe to boot you into the correct OS.

3.) Windows OS Loader: WinLoad.exe loads important drivers to kick start the Windows Kernel. The kernel uses the drivers to talk to the hardware and do rest of the things required for the boot process to continue.

4.) Windows NT OS Kernel: This is the last stage which picks up the Registry settings, additional drivers, etc. Once that has been read, the control is taken by the system manager process. It loads up the UI, the rest of the hardware and software. That’s when you finally get to see your Windows 10 Login screen.

When you run Windows 10 on a computer that supports Unified Extensible Firmware Interface (UEFI), Trusted Boot protects your computer from the moment you power it on. When the computer starts, it first finds the operating system bootloader. Computers without Secured Boot simply run whatever bootloader is on the PC’s hard drive. When a computer equipped with UEFI starts, it first verifies that the firmware is digitally signed. If Secure Boot is enabled, the firmware examines the bootloader’s digital signature to verify that it is intact hasn’t been modified.

I hope this information helped you to learn more about the Windows 10 Boot process.

First of all thanks DonnDon for helping me out but still it's not clear to me when the important DLL files like hal.dll and bootvid.dll and even system32k.sys or other files are loaded. 

And I also search on some other websites they are telling there are seven steps:

Which are-

1. PreBoot
2. Windows Boot Manager
3. Windows OS Loader
4. Windows NT OS Kernel
5. Session Initialization(SMSS.exe,Csrss.exe)

6.Winlogon Initialization(dwm.exe,wininit.exe)

7.Explorer InitializationI need information from Windows NT OS kernel to explorer initialization. You already gave me some information for Windows NT OS Kernel but I need more.

Thank you.