Stop 0xED or UNMOUNTABLE_BOOT_VOLUME

The kernel-mode I/O subsystem attempted to mount the boot volume and failed. This error might also occur during an upgrade to Windows 7 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 file system 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 the section titled "Stop Message Checklist" later in this tutorial.

• If you are using higher-throughput ATA disks and controllers, which are those capable of data transfer rates above 33.3 MB/sec, 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 MB/sec, but it is mandatory for higher transfer rates. The additional grounded pins are required to avoid data loss.
• Some firmware allows 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 the section titled "Stop 0x7B or INACCESSIBLE_BOOT_DEVICE" earlier in this tutorial.