MHDD

MHDD is a professional-grade, freeware hard drive diagnostic and repair utility developed by the Russian company Maysoft (often attributed to author Dimitry Postrigan). Unlike Windows-based tools, MHDD runs in a pure DOS environment and bypasses the motherboard BIOS to directly access IDE/SATA/SCSI ports, allowing it to interact with the drive’s physical sectors at a very low level. This makes it a staple for technicians performing surface scans and attempting bad sector repair.

Core Capabilities and Commands

MHDD operates primarily through command-line inputs within its DOS interface. Its key functions include:

• Surface Scanning (SCAN / F4): This is the most frequently used feature. It performs a block-by-block read verification of the drive surface, measuring access times. The results are displayed as colored blocks (grey/green for normal, red for bad or dangerously slow sectors). Key parameters include Start/End LBA, Timeout (threshold for marking a sector bad), and Remap (redirecting bad sectors to the drive’s spare G-list area).
• Drive Identification (ID / F2): Displays detailed drive information, including model, serial number, firmware version, LBA capacity, and supported DMA modes.
• Erase Functions: ERASE quickly wipes data (255 sectors at a time), while AERASE performs a slower, sector-by-sector wipe. Both are destructive and make data recovery impossible.
• Security Management: Commands like PWD (set password), UNLOCK (unlock with user password), and DISPWD (remove password) manage the drive’s ATA security features. Caution is required, as a forgotten password can render the drive inaccessible.
• Capacity Management: HPA reduces the drive’s visible capacity, while NHPA/RHPA restores or displays the true full capacity.

Workflow and Usage Notes

MHDD is typically booted from a DOS floppy, CD, or USB drive. The general workflow involves:

1. Starting the tool and selecting the target drive from the detected list.
2. Running ID (F2) to confirm the correct drive and check its basic health.
3. Running SCAN (F4) with Remap initially set to OFF to assess the extent of surface damage without making changes.
4. If bad sectors are found and the drive contains no critical data (or is backed up), re-running the scan with Remap set to ON to attempt repair by reallocating those sectors.

Key Cautions

• Data Loss Risk: Commands like ERASE, AERASE, and even SCAN with Remap enabled can cause irreversible data loss. Always back up important data before attempting any repair operations.
• Environment Constraints: MHDD must run in a pure DOS environment and generally should not be run from the drive being tested. It also requires the target drive to be connected to a supported interface (IDE/SATA/SCSI) that MHDD can detect directly.
• Not a Data Recovery Tool: MHDD is for diagnosing and attempting to repair the drive’s surface. It is not designed to reconstruct deleted files or partitions. For logical data recovery, tools like R-Studio or TestDisk are more appropriate.