Windows 9x Startup Files

You need to know the important system files that are involved in the system configuration in order to be able to diagnose problems with Windows machines. Windows 9x and Windows Me have similarities so most things here apply to Windows 95/98 and Me unless stated otherwise.

Important files in Windows are usually hidden by the operating system by default. To view these files in Windows Explorer it is necessary to "Show all hidden files". Some system files are stored in the root of the C drive, while others are stored in the WINDOWS directory, you'll discover that these files are exist purely for backwards compatibility whereas others affect the operation of your machine.

Windows Startup Files

• MSDOS.SYS - Primarily handles disk I/O, stays in memory all the time.
  
• EMM386.EXE - Allows Windows to control upper memory, this functionality is built into Windows Me.
  
• HIMEM.SYS - This is a Windows 9x file which is used to access high memory area (HMA).
  
• IO.SYS - Allows Windows to interact with the system hardware and BIOS. It also includes drivers for common hardware devices, ports and drives.
  
• WIN.INI - This file was used to store system settings such and communications drivers, wallpaper, screen saver etc for Windows 3.x, 95/98. This file has now been replaced by the Registry.
• WIN.COM - A file used by Windows 9x that initiates the protected load phase.
  
• SYSTEM.INI - This file was used to store system settings such and language, location etc for Windows 3.x, 95/98. This file has now been replaced by the Registry.
  
• COMMAND.COM - A command interpreter, or the DOS shell
  
• CONFIG.SYS - A file that is used in MS-DOS and early versions of Windows to load device drivers and control memory usage.
  
• AUTOEXEC.BAT - An automatically run batch file used to run commands on startup on MS-DOS and early versions of Windows. (more information about AUTOEXEC.BAT and CONFIG.SYS can be found here)
  

Editing non binary files such as AUTOEXEC.BAT can be achieved in a number of ways. Windows 95/98 provide a DOS tool called SYSEDIT, which essentially opens up a GUI with multiple text files allowing you to edit the following files:

• SYSTEM.INI
• CONFIG.SYS
• WIN.INI
• SYSTEM.INI
• PROTOCOL.INI (Windows 9x only)
  

Whereas Windows 98/Me introduce a new tool called MSCONFIG.EXE which achieves the same end only in a slightly more user-friendly fashion, both SYSEDIT and MSCONFIG can be run from the command prompt.