Important Startup Files

For Windows to start, the system and boot partitions must contain the files listed in Table-4.

Table-4 Windows Startup Files

File Name	Disk Location	Description
BootMgr	Root of the system partition	The Windows Boot Manager.
WinLoad	%SystemRoot%\System32	The Windows Boot Loader.
BCD	\Boot	A file that specifies the paths to operating system installations and other information required for Windows to start.
Ntoskrnl.exe	%SystemRoot%\System32	The core (also called the kernel) of the Windows operating system. Code that runs as part of the kernel does so in privileged processor mode and has direct access to system data and hardware.
Hal.dll	%SystemRoot%\System32	The HAL dynamic-link library (DLL) file. The HAL abstracts low-level hardware details from the operating system and provides a common programming interface to devices of the same type (such as video adapters).
Smss.exe	%SystemRoot%\System32	The Session Manager file. Session Manager is a user-mode process created by the kernel during startup. It handles critical startup tasks including creating page files and performing delayed file rename and delete operations.
Csrss.exe	%SystemRoot%\System32	The Win32 Subsystem file. The Win32 Subsystem is started by Session Manager and is required by Windows to function.
Winlogon.exe	%SystemRoot%\System32	The Logon Process file, which handles user logon requests and intercepts the Ctrl+Alt+Delete logon key sequence. The Logon Process is started by Session Manager. This is a required feature.
Services.exe	%SystemRoot%\System32	The Service Control Manager is responsible for starting and stopping services and is a required feature of Windows.
Lsass.exe	%SystemRoot%\System32	The Local Security Authentication Server process is called by the Logon Process when authenticating users and is a required feature.
System registry file	%SystemRoot%\System32 \Config\System	The file that contains data used to create the registry key HKEY_LOCAL_MACHINE\SYSTEM. This key contains information that the operating system requires to start devices and system services.
Device drivers	%SystemRoot%\System32 \Drivers	Driver files in this folder are for hardware devices, such as keyboard, mouse, and video.

In Table-4, the term %SystemRoot% is one of many environment variables used to associate string values, such as folder or file paths, to variables that Windows applications and services use. For example, by using environment variables, scripts can run without modification on computers that have different configurations. To obtain a list of environment variables that you can use for troubleshooting, type set at the Windows command prompt.

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Important Startup Files

Table-4 Windows Startup Files

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