Windows stop UNMOUNTABLE_BOOT_VOLUME error

Updated: 09/12/2023 by Computer Hope

The UNMOUNTABLE_BOOT_VOLUME or Stop 0x000000ED error message occurs when the I/O subsystem attempts to mount the boot volume and cannot.

The blue screen displays the following parameters in the Stop code:

  • 1 - The device object of the boot volume
  • 2 - The status code from the file system that describes why it failed to mount the volume
  • 3 - Reserved
  • 4 - Reserved

This error can be due to these reasons:

  • Your computer features a UDMA (Ultra Direct Memory Access) hard disk controller, and the hard drive uses a 40-wire connector cable to connect to the motherboard. Or, the BIOS (basic input/output system) is configured to force a faster UDMA mode than what is normally supported.
  • The file system is corrupted or damaged and cannot be mounted.

Checking the second parameter (0xbbbbbbbb) of the Stop code will identify what caused the error to occur. If the parameter is 0xC0000032, the error was caused by a damaged file system. If the parameter is not 0xC0000032, the error was caused by an issue with the UDMA hard disk controller.

UDMA hard disk controller issue

If the hard drive uses a 40-wire connector cable, replace the cable with an 80-wire, 40-pin connector cable. Restart the computer to see if the error re-occurs.

If the error is not resolved by replacing the connector cable, access the BIOS and load the 'fail-safe' default settings. Re-activate the frequently used options, like USB (universal serial bus) support.

Corrupt or damaged file system

If the file system is damaged or corrupt, it may be possible to fix the boot volume by running the chkdsk /r command at a DOS prompt. You can access the DOS prompt using a Windows startup disk or a Windows installation disk. Please note that using this command may result in some lost data, so it is advised you back up any personal files before proceeding.

After repairing the boot volume, check to see what hardware caused the file system damage. Repair or replace the offending hardware to prevent further file system damage.

Alternately, if the chkdsk /r command does not work, you can try the fixboot command at the DOS prompt.