Stop 0x000000ED or UNMOUNTABLE_BOOT_VOLUME

The kernel mode I/O subsystem attempted to mount the boot volume and it failed. This error might also occur during an upgrade to Windows XP Professional on systems that use higher throughput ATA disks or controllers with incorrect cabling. In some cases, your system might appear to work normally after you restart.

Interpreting the Message

This Stop message has two parameters:

1. Device object of the boot volume
2. Status code from the filesystem on why it failed to mount the volume

Resolving the Problem

The following suggestions are specific to Stop 0xED errors. For additional troubleshooting suggestions that apply to all Stop errors, see "Stop Message Checklist" later in this appendix.

• If using higher throughput ATA disks and controllers, those capable of data transfer rates above 33.3 megabytes per second, replace the standard 40-pin cable with an 80-pin cable. Using an 80-pin cable is optional for transfer rates up to and including 33.3 megabytes per second, but is mandatory for higher transfer rates. The additional grounded pins are required to avoid data loss.
• Some firmware enables you to force higher transfer rates even when you are using the incorrect cable type. Your firmware might issue a warning but allow the startup process to proceed. Restore the default firmware setting for ATA cable detection.
• Problems that cause 0xED errors might also cause Stop 0x7B errors. For more information about 0x7B Stop messages, see "Stop 0x0000007B or INACCESSIBLE_BOOT_DEVICE" earlier in this appendix.

For more information about Stop 0xED messages, see the Microsoft Knowledge Base link on the Web Resources page at http://www.microsoft.com/windows/reskits/webresources. Search using keywords winnt, 0x000000ED, and 0xED.