Corrupt MBR. Operating system: Unknown on (Unknown) Local Disk.

The computer in question was a Dell laptop with an mSATA SSD drive and a regular hard drive. Swapped out the mSATA with a larger one due to size constraints. Had to do the following:

• Cloned old mSATA drive to new, larger drive (fortunately the original mSATA was a Samsung PM800, one of the few supported by my adapter)
• Ran repair install on badly corrupted Windows 7 installation (took many hours of prep just to get it to this point)
• Computer came up fine after repair install. Ran some Windows Updates and rebooted
• After first reboot, it would not boot back up again
• Startup repair could not write back a new BCD

I think the boot/system partitions were oddly setup to begin with the previous configuration, including the active partition with the BCD being 700MB. Still do not know for certain what caused the booting issue. Also unsure what caused the original Windows corruption as the computer had been used in that state for what appears to have been a while.

I was brought in to fix an indexing issue but soon encountered services that would not start, MMC consoles could not be accessed, regsvr32 command could not be run, etc.

No S.M.A.R.T. issues on any drives mentioned.

At this point the computer is in ship shape and no indications of any other issues. User has all of their documents, programs, and settings in the state prior to repair install. No further Windows issues observed.

In my case (Windows 7), the root cause was that the BCD file was moved (by defragmentation perhaps???) to an area on the boot disk beyond sector 2,147,483,648 (the maximum 32-bit signed value), and Windows couldn't access it at boot time (that's the "a requested device is inaccessible" error).  In my case at least, the solution was to force the data for C:\Boot\BCD to reside on a sector within the two-billion-sector boot-time limit:

1. Boot into Windows recovery mode and bring up a command prompt (SHIFT-F10 is the shortcut key).
2. cd \Boot
3. If you tried startup repair already (which I'm sure you did), your original BCD file was renamed to BCD.Backup.0001.  In my case, the data in BCD file was still perfectly fine -- it just needed to be accessible by the Windows loader (i.e., within the boot-time sector limit).  What you want to do is locate an existing file that was installed at boot time, and therefore is certainly within the two-billion-sector limit, *AND* has enough space to contain the BCD data: 32K or greater in size.  I chose to use memtest.exe, so that's what I'll describe below.
4. Make a copy of your original memtest.exe: copy memtest.exe memtest.exe.org.
5. Copy your renamed BCD file to memtest.exe: copy BCD.Backup.0001 memtest.exe. Windows will reuse the existing sectors in the destination file if it can, and since memtest.exe is larger than 32K (the size of BCD), the entire BCD file will fit in memtest.exe's original sector space.
6. Rename memtest.exe to BCD.
7. Now rename memtest.exe.org memtest.exe.  What you have done in effect is move memtest.exe to another area on the disk and use memtest.exe's original sectors (which are inside the boot-time sector limit) to hold your BCD file.
8. Now ALT-TAB back to the repair options GUI and run startup repair again (you may not need to do this if your original BCD data is still OK, but I did it anyway); the repair step should work this time and the system should reboot.
9. The system should boot normally now!  :)

That worked for me, and I was about at my wit's end!  That's a nasty bug that Windows should fix -- it should "lock" the boot-time files and not allow them to be moved beyond the two-billion-sector-limit accessible the boot subsystem. One final note: whichever file you choose to reuse (memtest.exe in my case) will end up being moved to a different sector range, which will quite possibly be beyond the boot-time sector limit.  If that happens, memtest.exe would not be accessible by the boot subsystem (just like BCD was not).  So you may want to pick a different file to reuse, but whatever file you choose must already reside within the first two billion sectors on the disk and be >= 32K in size.

The real fix is that Windows should lock the boot-time files to be within the two-billion-sector limit so that the loader can always access them!  This is a really nasty bug.  I'm just glad to have my system back!

I doubt if the disk or the controller has gone bad. My disk was set up for a dual boot into Vista or Ubuntu. In doing a restore from Vista the  MBR became corrupt. I was still able to boot into Ubuntu and run perfectly but the Vista partition was not recognized even after using disk recovery tools on the Vista disk or from WD. Reinstallation of the Windows REQUIRED that I reformat the prior WinVista partition before it would install. Gotta love Vista !

Hi,

Boot from a Vista disk and run these :

bootrec /fixmbr

bootrec /fixboot

bootrec /scanos

bootrec /rebuildbcd

How to use the Bootrec.exe tool in the Windows Recovery Environment to troubleshoot and

repair startup issues in Windows Vista

http://support.microsoft.com/kb/927392

If those don't help you can "try" the diagnostics from the drive's maker.

Diagnostic Utilities By Manufacturer - run the one for your hard drive

http://www.techsupportforum.com/hardware-support/hard-drive-support/462298-no-ide-device-found.html

Corrected list as of 6-09-2010

Fujitsu Hard Drives: Diagnostic Utilities Here

http://www.fujitsu.com/emea/products/hdd/

Hitachi Hard Drives: Diagnostic Utilities Here

http://www.hitachigst.com/support/downloads/

IBM Hard Drives: Use Hitachi Utilities*

Toshiba Hard Drives: Use Hitachi or Maxtor Utilities

Maxtor Hard Drives: Diagnostic Utilities Here (now SeaGate)

http://www.seagate.com/www/en-us/support/

Quantum Hard Drives: Use Maxtor Utilities

Seagate Hard Drives: Diagnostic Utilities Here

http://www.seagate.com/www/en-us/support/downloads

Conner Hard Drives: Use Seagate Utilities

Samsung Hard Drives: Diagnostic Utilities Here

http://www.samsung.com/global/business/hdd/

Western Digital Hard Drives: Diagnostic Utilities Here

http://support.wdc.com/product/download.asp?lang=en

The trial versions of one of these "might" help.

SpeedFan

http://www.almico.com/sfdownload.php

HD Tune

http://www.hdtune.com/

Hope this helps and Happy Holidays!

Rob Brown - MS MVP - Windows Desktop Experience : Bicycle - Mark Twain said it right.