12.6 Windows 9x/2000 Registry Problems
12.6.1 The Registry files
The Registry files contain all the system configuration information. This includes the local hardware configuration, the network environment, file associations, and user configurations. USER.DAT and SYSTEM.DAT are the Registry files that contain all of the contents in the Registry.
  • USER.DAT – The USER.DAT file contains all of the information that is specific to the user. For example, this file is used to maintain user profiles, such as mouse speed, wallpaper, or color scheme.
  • USER.DA0 – When Windows successfully boots up the USER.DA0 file is created. This file is a back up of the USER.DAT file. If the USER.DAT file gets corrupted or is erased for some reason, rename the USER.DA0 file to USER.DAT and the registry can be restored.
  • SYSTEM.DAT – The SYSTEM.DAT file holds hardware, computer-specific profiles, and setting information. For example, every time a new piece of hardware is installed such as a video card, the information in the SYSTEM.DAT file is updated.
  • SYSTEM.DA0 – Like the USER.DA0 file, the SYSTEM.DA0 also gets created when Windows successfully boots. This file is a back up of the SYSTEM.DAT file. If the SYSTEM.DAT file gets corrupted or is erased for some reason, rename the SYSTEM.DA0 file to SYSTEM.DAT and the registry can be restored.
  • SYSTEM.INI – The SYSTEM.INI file contains hardware-setting information for the drivers that Windows uses for configuration. When the operating system needs to reference information about the hardware, it uses the SYSTEM.INI file.
  • WIN.INI – The WIN.INI file contains parameters that can be altered to change the Windows environment or software settings to suit the user's preferences. The WIN.INI file is a software initialization file for Windows. It contains information about some Windows defaults, the placement of windows, the color settings for the screen, available ports, printers, fonts, and software applications.
Note: WIN.COM is another registry file that controls the initial environment. It checks and loads Windows 95 core components when Windows 95 is loading.