Windows 95 Drive Repair: ScanDisk for Windows

When Microsoft released Windows 95, it transitioned users from a command-line interface to a modern graphical environment, introducing ScanDisk for Windows (scandskw.exe) to replace the real-mode MS-DOS ScanDisk utility for everyday drive maintenance. While Microsoft initially introduced the text-based ScanDisk in MS-DOS 6.2 to replace the rudimentary CHKDSK command, Windows 95 required a specialized tool capable of managing 32-bit operations, background multitasking, and the operating system's new file naming structures.

The Shift to a Graphical Interface

ScanDisk for Windows brought drive diagnostics directly into the Windows desktop environment. Rather than forcing users to reboot into real-mode DOS to verify disk integrity, the new utility was accessible straight through Windows Explorer:

  • Location: Accessible by right-clicking a drive, selecting Properties, navigating to the Tools tab, and clicking Check Now.
  • Executable: The graphical utility ran via scandskw.exe, distinct from the 16-bit scandisk.exe executable retained for DOS mode.
  • User Experience: It provided a visual progress bar, interactive dialog boxes for error resolution, and readable summary logs, eliminating the need to memorize command-line switches.

Critical Need: Support for Long File Names (VFAT)

The primary technical driver for replacing the standard MS-DOS utility was Windows 95’s introduction of Virtual File Allocation Table (VFAT), which brought Long File Names (LFNs) of up to 255 characters to the FAT16 file system.

Older DOS repair utilities, including previous versions of MS-DOS ScanDisk and CHKDSK, did not recognize the directory entries used to store LFNs. Running an older DOS utility on a Windows 95 volume often resulted in the utility misidentifying long-name metadata as disk corruption, inadvertently stripping file names down to their standard 8.3 format. ScanDisk for Windows was built natively to parse, validate, and preserve VFAT entries.

Core Features and Testing Modes

ScanDisk for Windows provided two primary scanning modes to address different levels of storage degradation:

  • Standard Test: Inspected the drive’s logical file allocation tables, directory structures, and file system integrity for issues such as lost clusters and cross-linked files.
  • Thorough Test: Performed all Standard checks while adding a physical surface scan to locate bad sectors on the disk, reading and relocating data away from failing sectors.
  • Automated Repair Options: Users could select "Automatically fix errors" to let the software convert orphaned allocation units directly into .CHK files in the root directory without pausing for user intervention.

The Remaining Role of MS-DOS ScanDisk

Although ScanDisk for Windows became the primary maintenance interface inside the operating system, an updated 16-bit version of MS-DOS ScanDisk was retained on the system. This version was updated to safely handle VFAT entries during pre-boot operations. If the system crashed or experienced an improper shutdown, the MS-DOS version executed automatically during the next boot sequence before the Windows graphical environment initialized, ensuring the disk was stable enough to load the desktop.