{"id":916,"date":"2013-08-27T15:11:11","date_gmt":"2013-08-27T20:11:11","guid":{"rendered":"http:\/\/neosmart.net\/kb\/?p=916"},"modified":"2016-07-11T07:43:33","modified_gmt":"2016-07-11T12:43:33","slug":"unmountable-boot-volume","status":"publish","type":"post","link":"https:\/\/neosmart.net\/wiki\/unmountable-boot-volume\/","title":{"rendered":"UNMOUNTABLE BOOT VOLUME BSOD: Fix for Windows XP, Vista, and 7"},"content":{"rendered":"

Information about the cause and possible resolutions of boot-related Blue Screen of Death (BSOD) with error “UNMOUNTABLE_BOOT_VOLUME<\/strong>”\u00a0and stop code STOP: 0x000000ED<\/code>.<\/p>\n

This error is sometimes misspelled as UNMOUNTABLE_BOOT_DRIVE, but is functionally the same.<\/p>\n

About “UNMOUNTABLE BOOT VOLUME”<\/h2>\n

The following information on this error has been compiled by NeoSmart Technologies, based on the information gathered and reported by our global network of engineers, developers, and technicians or partner organizations.<\/p>\n

Description and Symptoms<\/h3>\n

The error messages, alerts, warnings, and symptoms below are tied to this error.<\/p>\n

Symptom 1: BSOD with error UNMOUNTABLE_BOOT_VOLUME<\/h4>\n

Upon starting a PC running Windows XP, Windows Vista, or Windows 7, a blue screen of death (BSOD) may be encountered with the error message “UNMOUNTABLE_BOOT_VOLUME” and usually with a stop code of\u00a0STOP: 0x000000ED<\/code>, similar to the screen shown below:<\/p>\n

\"Blue<\/p>\n

The full text of this error is written below:<\/p>\n

A problem has been detected and Windows has been shut down to prevent damage\r\nto your computer.\r\n\r\nUNMOUNTABLE_BOOT_VOLUME\r\n\r\nIf this is the first time you've seen this error screen,\r\nrestart your computer. If this screen appears again, follow\r\nthese steps:\r\n\r\nCheck to make sure any new hardware or software is properly installed.\r\nIf this is a new installation, ask your hardware or software manufacturer\r\nfor any Windows updates you might need.\r\n\r\nIf problems continue, disable or remove any newly installed hardware \r\nor software. Disable BIOS memory options such as caching or shadowing.\r\nIf you need to use Safe Mode to remove or disable components, restart\r\nyour computer, press F8 to select Advanced Startup Options, and then \r\nselect Safe Mode.\r\n\r\nTechnical Information:\r\n\r\n*** STOP: 0x000000ED (0x80F128D0, 0xc000009c, 0x00000000, 0x00000000)<\/pre>\n
Symptom 2: BSOD with error UNMOUNTABLE_BOOT_VOLUME<\/h4>\n
A variation of symptom 1, with this possible alternate text is this:<\/p>\n
\"Blue<\/p>\n
The text of this error:<\/p>\n
A problem has been detected and Windows has been shut down to prevent damage\r\nto your computer.\r\n\r\nUNMOUNTABLE_BOOT_VOLUME\r\n\r\nIf this is the first time you've seen this error screen,\r\nrestart your computer. If this screen appears again, follow\r\nthese steps:\r\n\r\nCheck to be sure you have adequate disk space. If a driver is \r\nidentified in the Stop message, disable the driver or check \r\nwith the manufacturer for driver updates. Try changing video \r\nadapters.\r\n\r\nCheck with your hardware vendor for any BIOS updates. Disable \r\nBIOS memory options such as caching or shadowing. \r\nIf you need to use Safe Mode to remove or disable components, restart \r\nyour computer, press F8 to select Advanced Startup Options, and then \r\nselect Safe Mode.\r\n\r\nTechnical Information:\r\n\r\n*** STOP: 0x000000ED (0x80F128D0, 0xc000009c, 0x00000000, 0x00000000)<\/pre>\n
Causes of this Error<\/h3>\n
A blue screen of death with the UNMOUNTABLE BOOT VOLUME error is an indication that Windows was unable to mount the boot filesystem1<\/a><\/sup> to read\/load required dependencies from it.<\/p>\n
While Windows, being based off a largely microkernel-esque architecture, can load dependencies and components dynamically, there is a basic subset of dependencies that absolutely must be brought online during the boot procedure or else Windows will fail to boot, even if the kernel has been invoked.<\/p>\n
With the latest versions of Windows, and especially after the kernel and driver restructuring that took place during the development of Windows Vista, this list of components has steadily dwindled and now comprises only the most basic (and largely universal) input\/output drivers2<\/a><\/sup> in addition to the controllers for the hard disk driver.<\/p>\n
If Windows is unable to identify and interface with the hard disk controller (whether integrated into the motherboard or as a drop-in PCI-E card) or if hard disk controller is brought online successfully but Windows cannot read the volume it is being booted from for a variety of reasons, a BSOD featuring the UNMOUNTABLE BOOT VOLUME error may present.<\/p>\n
This error has been known to occur as a result of one or more of the following:<\/p>\n
Cause 1: Failed\/Incompatible disk controller drivers<\/h4>\n
As explained above, if Windows is unable to identify and interface with the hard disk controller responsible for the drive the system partition resides on, the Windows kernel won’t be able to read and load the basic dependencies from disk and this blue screen will be encountered.<\/p>\n
A common cause that’s often responsible for this scenario is an uninstall or failed update\/upgrade of the hard disk controller drivers.<\/p>\n
For instance, if the Intel or LSI disk management drivers are removed, corrupted, uninstalled, or incorrectly upgraded and Windows does not already have “native,” basic support for the particular hard disk controller in use, it will be unable to communicate with the disk adapter to read the required data resulting in the UNMOUNTABLE BOOT VOLUME blue screen of death.<\/p>\n
Cause 2: Attempt to load Windows from wrong partition<\/h4>\n
Another scenario where Windows will be unable to load its core drivers and other basic dependencies would be in a situation where Windows\u00a0has<\/em> the required drivers to interface with the hard disk controller, but is instructed to load itself from the wrong partition (i.e. not the partition it is actually installed to). When the bootloader (either NTLDR in the case of Windows XP or BOOTMGR in the case of Windows Vista and Windows 7) begins to load an operating system based on the configuration file3<\/a><\/sup> it passes along to the kernel (in the environment block) information about where it should load the operating system from.<\/p>\n
If the configuration store (BOOT.INI\/BCD) is incorrectly set or no longer points to the correct partition, the ntoskrnl will be unable to load Windows from the indicated partition and an UNMOUNTABLE BOOT VOLUME BSoD may occur.<\/p>\n
Cause 3: Windows partition resized or moved<\/h4>\n
In a similar vein to the situation with an incorrectly-configured BCD or BOOT.INI that directs the Windows kernel to load the operating system from the wrong partition, the UNMOUNTABLE BOOT VOLUME error may also occur if the identifier for the Windows partition is changed but the boot configuration file retains the outdated information.<\/p>\n
NTLDR and BOOTMGR both have multiple methods of uniquely identifying (or trying to) a partition, some of which are based off a combination of the disk number and the partition offset (how far from the start of the disk) or partition number (how many partitions precede it either physically in the sequential disk layout or in the partition table in the MBR).<\/p>\n
If the Windows partition is moved, a partition is added or removed\u00a0before<\/em> the Windows partition on disk, or the order of the disks changes, the BCD or BOOT.INI references to the Windows partition may no longer be correct and the kernel will throw the UNMOUNTABLE BOOT VOLUME blue screen when it attempts to load Windows from the wrong partition.<\/p>\n
Cause 4: Changed or reconfigured SATA AHCI\/IDE\/RAID mode<\/h4>\n
Similar to the first situation discussed above wherein the necessary device drivers for communicating with the Windows partition have been uninstalled or incorrectly replaced, it is possible for the drivers that Windows has been configured to load and use at the very start of the boot procedure are no longer correct \u2014 even though the underlying hardware has not changed. Most SATA controllers (the onboard Intel ICH ACH controllers, Marvell, JMicron, nVidia, and others) expose an option in the BIOS for the disk controller to be configured in any one of three modes: IDE, AHCI, or RAID.<\/p>\n