Revert a Disk to Basic Disk

Extended partitions, OEM partitions and type 0x42 for dynamic volumes. However, if MBR contains any invalid partition type, your system might run into an issue. At times, when you observe that disk is appearing as ‘Dynamic Unreadable’, it simply indicates that MBR contains invalid partition type that dynamic disks don’t support. It usually occurs when the MBR is damaged or improperly altered. Thus, to restore the lost information in this way, you require using your recent data backup. However to cope up with the situations that might occur due to data backup unavailability or damage, you should use Disk Recovery tools for recovery purpose.

You might observe following symptoms while using a Windows XP, Server 2003 or 2000 based system:

-You open Disk Management snap-in and disk appears as ‘Dynamic Unreadable’

-You try to use Revert to Basic Disk option and get an error that it will cause data loss. Next, you click yes to the option, but the process fails

-You try to use Diskpart.exe utility for converting the disk to a basic disk. You get a false message stating that it has been successfully converted into basic disk. Next, you rescan the disk, but it still appears ad ‘Dynamic Unreadable’

Cause

Basic causes responsible for this behavior to occur are:

-You are running Windows earlier than Windows 2000 and have deleted or recreated the partition using Fdisk.exe. This causes the disk to appear as damaged dynamic disk and prevent you to convert it back to basic disk

-MBR or EBR is corrupted and is forcing to appear a basic disk as damaged dynamic disk. It can occur if MBR or EBR contains a hexadecimal 0x42 value.

Solution

Follow these steps to solve the existing issue:

-Use Diskmap.exe or Dmdiag.exe utility in verbose mode to output MBR information containing system IDs and partition types in hexadecimal format.

-If this information contains invalid types, you should next use clean command of Dskprobe.exe or alternatively, Diskpart.exe utility to remove all disk partitions.

-The above step will delete all the data from the disk, so use your recent data backup to restore. In case of any backup concerns, scan your disk using Data Recovery tools. These are powerful hard disk recovery tools built to scan and safely recover the lost information.