MBR Partition Table
What Is the MBR Partition Table?
The MBR Partition Table is a 64-byte structure stored inside the Master Boot Record (sector LBA 0) of an MBR-formatted disk. It defines how storage space is divided and tells the system where each partition begins and ends. Unlike GPT, which stores multiple redundant partition tables, the MBR Partition Table has only one copy, making it highly vulnerable to corruption.
The table contains four 16-byte partition entries, meaning an MBR disk supports up to four primary partitions (or three primaries + one extended partition containing logical volumes).
When the MBR Partition Table becomes damaged, the system cannot map partitions correctly, causing them to disappear, appear as RAW, or show incorrect size information.
Supports Windows 7/8/10/11 and Windows Server
Table of Contents
Structure of an MBR Partition Entry (16 bytes)
Each entry stores:
- Boot flag (1 byte) — indicates active/bootable partition
- Starting CHS address (3 bytes)
- Partition type ID (1 byte) — e.g., NTFS, FAT32, Linux
- Ending CHS address (3 bytes)
- LBA start sector (4 bytes)
- Partition size (4 bytes)
Because these offsets determine how Windows interprets the entire disk, even a single altered byte may cause severe partition visibility issues.
Symptoms of a Damaged MBR Partition Table
Common issues include:
- Partitions missing from File Explorer
- Disk showing as Unallocated or RAW
- Wrong partition size or incorrect file system label
- PC unable to boot
- System stuck at a blinking cursor
- Drive recognized in BIOS but not in Windows
Although alarming, these issues often indicate structural damage—not actual deletion of user files.
Causes of Partition Table Damage
Damage can occur due to:
- Power loss during partition updates
- Malware or boot-sector viruses
- Incorrect disk cloning or imaging
- Faulty external HDD disconnections
- Bad sectors affecting LBA 0
- Third-party tools rewriting the layout
- Accidental initialization or repartitioning
Since the MBR Partition Table lacks redundancy, repair requires caution.
How to Repair an MBR Partition Table (Step-by-Step)
1. Avoid Formatting or Initializing the Disk
If Windows states “You need to format the disk” or prompts to initialize it as GPT/MBR, cancel immediately.
Formatting replaces partition entries, risking permanent metadata loss.
2. Inspect the Disk in Windows Disk Management
If the disk appears as RAW or Unallocated, the partition table may be unreadable.
But the data inside the partition region often remains untouched.
3. Use Windows Recovery Environment (for boot drives)
If the system cannot boot:
- Boot from Windows installation media
- Open Command Prompt
- Run:
bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd
These commands repair the bootloader but do not rebuild the partition table.
They help only if the boot entry, not the table itself, is corrupted.
4. Rebuild the MBR Partition Table
Partition recovery tools like DiskDrill or Minitool can detect file systems and rebuild the partition table automatically. Make sure the tool doesn’t format the partitions in case of data loss.
5. Recover Data Before Making Structural Modifications
If the partition table is severely corrupted, the safest option is to extract data before rebuilding the table.
Tools like Magic Data Recovery read file system signatures directly, bypassing damaged MBR structures. Even if the disk appears RAW or unrecognized, the software can scan sectors, locate NTFS/MFT metadata, and recover intact files.
6. Avoid CHKDSK on Partition-Table-Damaged Drives
CHKDSK can modify or delete orphaned records and should not be used until the file system is confirmed consistent.
MBR Partition Table vs. GPT
Feature | MBR | GPT |
Max partitions | 4 primary | 128+ |
Max disk size | 2 TB | Up to 9.4 ZB |
Backup table | None | Yes (header + backup) |
Boot mode | Legacy BIOS | UEFI |
Corruption resistance | Low | High |
A key limitation of MBR is the lack of partition table redundancy, making corruption more destructive.
Conclusion
The MBR Partition Table is essential for interpreting disk layout, and damage to this 64-byte structure can cause missing partitions, RAW disks, or boot failures.
Fortunately, the data inside the partitions is often still intact.
By avoiding formatting, using proper reconstruction methods, and recovering data before applying structural changes, users can safely restore access.
When the drive becomes unrecognized or RAW, Magic Data Recovery provides a reliable, read-only method to extract files before repairing the disk.
Supports Windows 7/8/10/11 and Windows Server
FAQs for MBR Partition Table
Can a corrupted MBR Partition Table be repaired without losing data?
Why does my MBR disk show as Unallocated?
Can the Partition Table be restored manually?
Does rebuilding the MBR also rebuild the partition table?
Can software recover files if the partition table is destroyed?
Can bad sectors damage the MBR Partition Table?
Should I convert from MBR to GPT to fix the issue?
