Windows startup process

The Windows startup process is the process by which Microsoft's Windows series of operating systems initializes.

In Windows versions 1.01 to Windows/386, the system was loaded when WIN.COM was executed. It then loaded WIN100.BIN or WIN200.BIN and WIN100.OVL or WIN200.OVL, along with the configuration settings file WIN.INI. The default shell is the MS-DOS Executive.

The modules GDI.EXE, KERNEL.EXE and USER.EXE, fonts, and the various device drivers (such as COMM.DRV, MOUSE.DRV, KEYBOARD.DRV) are incorporated in WIN100.BIN/WIN200.BIN and WIN100.OVL/WIN200.OVL.

In Windows 3.x and 95/98/ME, the boot loader phase is handled by MS-DOS. During the boot phase, CONFIG.SYS and AUTOEXEC.BAT are executed, along with the configuration settings files WIN.INI and SYSTEM.INI. Virtual device drivers are also loaded in the startup process: they are most commonly loaded from the registry (HKLM\System\CurrentControlSet\Services\VxD) or from the SYSTEM.INI file.

When all system configuration files and device drivers have been loaded, the 16-bit modules, KRNL386.EXE, GDI.EXE, and USER.EXE, are loaded, then the 32-bit DLLs (KERNEL32.DLL, GDI32.DLL, and USER32.DLL) are loaded. The 32-bit VxD message server (MSGSRV32) starts MPREXE.EXE, which is responsible for loading the network logon client (such as Client for Microsoft Networks, Microsoft Family Logon or Windows Logon).

When a user is logging on to Windows, the startup sound is played, the shell (usually EXPLORER.EXE) is loaded from the [boot] section of the SYSTEM.INI file, and startup items are loaded.

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