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Windows BOOT Sequence


Boot Order has 7 steps:

Step 1 – Master Boot Record (MBR)

  • Reads & loads the partition boot sectors

Step 2 – Boot Sector

  • Reads root directory to load NTLDR

Step 3 – NTLDR

  • Turns on paging
  • Reads Boot.ini
  • Presents Boot Menu
  • Loads NTOSKRNL.exe
  • Bootvid.dll
  • Hal.dll
  • Boot start Device Drivers

Step 4 – NTOSKRNL.exe

  • Initalises Executive subystems
  • System start Device Drivers
  • Runs SMSS.exe

Step 5 – SMSS

  • Loads Win32 Subsystem
  • Win32k.sys
  • CSRSS.exe
  • Winlogon.exe – started


  • Starts Service Control Manager (SCM)
  • Local Security Subsystem (LSASS)
  • LSA generates the Token (includes User SID, Group SID, Impersonation Rights, privileges and expiry time of Token)
  • Presents Interactive Logon Dialogue Box

Step 7 – Service Control Manager (SCM)

  • Loads Auto start Device Drivrs
  • Win32 services


What are device drivers?

Device drivers are loadable KERNEL MODE modules (end in .sys) that interface between the I/O Manager and the hardware.  They run in KERNEL mode, in 3 contexts (User thread, Kernel system thread or interrupt).


Device drivers – call the HAL (Hal.dll)

HAL – calls the hardware.

They don’t manipulate hardware directly, they call functions in the HAL to interface to the Hardware.


There are several types of device drivers:

1. Hardware drivers manipulate hardware (using the HAL) to write to physical device.

2. File system drivers – accepts file oriented I/O requests.

3. File System FILTER drivers – Encryption, Disk mirroring, intercept I/O’s

4. Network redirectors – transmit file system I/O requests to the network

5. Protocol drivers – implement networking protocols such as TCP/IP, NetBeui etc

6. Kernel Streaming FILTER drivers – chained together to perform signal processing on data streams, recording or displaying audio or video.

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