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Windows 9X Boot Sequence

Important Boot Files

The Msdos.sys file contains basic information about the location of the Windows folder and startup files, and other options. Some of these options can be edited using the Advanced Troubleshooting Settings tab in System Configuration Utility.

For more information about the Msdos.sys file, see the following article in the Microsoft Knowledge Base:

ARTICLE-ID: Q118579

TITLE : Contents of the Windows Msdos.sys File

The Config.sys file is provided for backwards compatibility with MS-DOS- based and older Windows-based programs and may not be present on your computer. It loads low-level MS-DOS-based drivers, many with a system (.sys) extension.

The Autoexec.bat file is also provided for backwards compatibility with MS-DOS-based and older Windows-based programs and may not be present on your computer. It loads MS-DOS-based programs, often with .com and .exe extensions.

The Winboot.ini file is a temporary version of the Msdos.sys file that may be present if a program is making changes to your computer that may affect the boot process. Under normal conditions, it is deleted after the program is complete, resides in the root directory, and overrides settings in the Msdos.sys file.

The Winstart.bat file may not be available as a check box on the General tab in System Configuration Utility. The Winstart.bat file is created for programs that need to run an MS-DOS-based program to enable functionality of a Windows-based program. Most users do not have this program.

The System.ini file contains information about your computer's settings for specific hardware. This file must be present in the Windows folder for Windows to start. It is used to load various drivers including sound and video adapter drivers. It may also contain additional 16-bit drivers for hardware does not use 32-bit drivers.

When you click to clear the Process System.ini File check box in System Configuration Utility and restart your computer, the following changes take place:

  1. Your display is set to a resolution of 640 X 480 pixels with 16 colors. If you had the display set to a higher resolution, shortcuts on the desktop may overlap.
  2. Your sound card no longer operates correctly.

The Win.ini file contains information specific to the overall appearance of Windows. This file must be present in the Windows folder or it is re-created by Windows, is read at startup for backwards-compatibility with Windows 3.x, and many of the settings are duplicated in the registry. When you clear the Process Win.ini File check box in System Configuration Utility, a generic version of the Win.ini file is created.

The Wininit.ini file is used to complete the installation of various components for Windows and third-party products. Each time a program needs to copy or remove a file that is in use, instructions are written to the Wininit.ini file. Windows checks for the presence of the Wininit.ini file during the boot process and, if found, performs the instructions. Rename this file to troubleshoot problems, if present.

The System.dat file is one of two registry files that are required to start Windows. The System.dat is similar to the System.ini file, containing computer and software settings. The Load Startup Group option contains the entries that are loaded from the System.dat portion of the registry.

The User.dat file is the second of two registry files that are required to start Windows. The User.dat file is similar to the Win.ini file in that it contains information for running specific programs and information about the overall appearance of Windows.

You can use System Configuration Utility to create a backup of the startup files described in this article. To do so, click Create Backup on the General tab in System Configuration Utility. You can choose to save the files to a folder on one of your hard disks, or save it to a floppy disk (recommended).

Static .vxd files are used to load virtual hardware and software drivers. Many third-party manufacturers add their own virtual drivers (static .vxd files).