Windows 98 User Profiles on Shared Computers

This article examines how Microsoft Windows 98 handled and stored individual user profiles on shared computers. In environments where multiple people used the same machine, Windows 98 separated user environments by creating dedicated directory trees within the file system and partitioning the Windows Registry into machine-wide and user-specific configuration files. While this system allowed personalized desktops, settings, and application preferences, it was designed primarily for convenience and personalization rather than robust access control or security.

Enabling Multi-User Support

Windows 98 did not enforce multi-user profiles by default. During a standard installation, the operating system maintained a single, shared configuration located directly in the root of the Windows directory.

To enable individual profiles, an administrator or user had to configure the settings via Control Panel > Passwords > User Profiles. Users could select whether to customize individual Desktop settings, Start Menu programs, Network Neighborhood contents, and Internet Favorites. Once enabled, Windows 98 prompted users with a login dialog upon system startup.

File System Directory Structure

When multi-user support was enabled, Windows 98 generated a dedicated folder hierarchy for each registered user inside the primary operating system directory, usually located at:

C:\WINDOWS\Profiles\<Username>\

Inside each user's specific folder, Windows 98 stored customized versions of shell folders and application configurations:

  • Desktop: Contained the user's customized desktop icons and shortcuts.
  • Start Menu: Stored shortcuts specific to the user's customized application menus.
  • Favorites: Contained the user's saved Internet Explorer bookmarks.
  • Recent: Tracked the user's recently accessed documents and media.
  • Application Data: Preserved user-specific application preferences and cache files.
  • My Documents: Often redirected to a profile-specific folder depending on the configuration.

Files and shortcuts not placed in a user's dedicated profile remained global, located in the primary C:\WINDOWS\ subfolders, ensuring that system-wide software installations remained accessible to everyone.

Registry Separation: USER.DAT and SYSTEM.DAT

Windows 98 divided its registry database into two core files to maintain separation between hardware configurations and individual preferences:

  1. SYSTEM.DAT: Stored in the root C:\WINDOWS\ directory, this file managed machine-level configurations, hardware drivers, installed software definitions, and global system parameters (mapped to HKEY_LOCAL_MACHINE).
  2. USER.DAT: When multi-user support was turned on, a distinct USER.DAT file was created inside each user's profile folder (C:\WINDOWS\Profiles\<Username>\USER.DAT). This file held personal preferences, such as window color schemes, wallpapers, mouse cursor themes, and per-user application settings.

Upon a successful login, the operating system loaded the respective user's USER.DAT file into memory and mounted it under the HKEY_CURRENT_USER registry hive.

Security Limitations

Windows 98 operated on top of the MS-DOS foundation and used the FAT16 or FAT32 file systems, which lacked Access Control Lists (ACLs) and file-level encryption. Consequently, the user profile implementation provided environment personalization rather than data security:

  • Users could easily open File Manager or Windows Explorer and browse, edit, or delete files stored in another user's profile under C:\WINDOWS\Profiles\.
  • Clicking Cancel or pressing the Escape key at the Windows 98 logon prompt simply bypassed the user-specific profile load, dropping the user onto the machine using the default system profile while retaining full read and write access to the entire hard drive.