# [SOLVED] W7 system partition drive letter changed won't boot



## wc00 (May 3, 2007)

I am trying to help a friend. 

I built a desktop computer for him, Dec 2011.
W7 Home Premium SP1
HDD haD a single partition, C:, onto which I installed W7, using a legitimate, commercial W7 DVD.
W7 was activated. Updates were downloaded & installed using W7's automatic update feature. 

HDD is SATA, 1 TB

The HDD is seen by the BIOS; within the BIOS and from the boot menu. 

16 Aug 2012, the computer worked properly; shut down normally. 

The next time he turned the PC on, 19 Aug 2012, the boot process proceeded through the Windows 7 splash screen. 

NO login screen appeared. 

Spontaneous reboot. 

W7's automatic repair screen appeared, advising that W7 could not be repaired. 

Things I have tried:
System Restore point; tried twice.
1 restore point, for 15 Aug, notes Windows Update. 

System Restore advised that it looked at the D: drive for restore points. None found. 

Rebooted to W7 repair tool.
Command prompt. 

C:\ dir
no files nor folders

D:\ dir
files & folders are present


X:bootrec /scanos
NO Windows Installations found

X:bootrec /fixmbr
X:bootrec /fixboot
X:bootrec /rebuildbcd

Reboot
Same problem

Rebooted to W7 repair tool.
Command prompt.
X:bootrec /scanos
NO Windows Installations found

Reboot
No Joy

Rebooted to W7 repair tool.
Command prompt.

c:bootrec /fixmbr
c:bootrec /fixboot
c:bootrec /rebuildbcd

Reboot
Same problem

Rebooted to W7 repair tool.
Command prompt.
X:bootrec /scanos
NO Windows Installations found

Reboot
No Joy

Rebooted to W7 repair tool.
Command prompt.

d:bootrec /fixmbr
d:bootrec /fixboot
d:bootrec /rebuildbcd

Reboot
No Joy

Rebooted to W7 repair tool.
Command prompt.
d:bootrec /fixmbr
d:bootrec /fixboot

d:bootsec.exe /nt60 all /force

After each instance of using bootrec and bootsec.exe, I have been informed that the operation completed successfully. 


After each attempt at repairing W7, the computer boots beyond the W7 splash screen, but the W7 login screen does not appear. 

I also tried "Last known good configuration". 

Booted to optical drive with UBCD4Win CD, which I had made probably before W7 was released. 

The HDD was not present in Computer / My Computer. 

1. If this can be fixed without a re-format / re-install, please tell me how. 

2. If the fix requires a re-format / re-install, which tool can I use to copy my friend's data to an external drive? 

I read about the Paragon Recovery CD, but I have never used it. 

Thanks for your attention to this problem. 

wc00


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, boot to the RE (repair your computer) at the x:\sources prompt type:-

bcdedit (press enter) this will reveal the boot manager and the boot loader that your OS uses to boot. Note down the entries, next type:-

bcdedit | find "osdevice" (press enter) this tells us what drive letter the RE has assigned the OS, not always C: 

It will be this drive letter that you will need to use to repair the boot .


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

D:

That doesn't surprise me. 

As noted, above:
"System Restore advised that it looked at the D: drive for restore points. None found. 
"

"C:\ dir
no files nor folders

D:\ dir
files & folders are present
"

wc00


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

I disabled, temporarily, the automatic restart and this appeared.

STOP C000021a Fatal System Error
The verification of a knownDLL failed.
Status of 0xC000021f

wc00


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, what did you get from the bcdedit cmd, this is what your current boot loader will look like. Normally you can copy this to notepad however as you cannot boot we won't be able to read it, maybe just copy it down as best you can what does it see the partition as and device and os device under boot loader?


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

???

Per your instructions, I ran bcdedit & located the os. 

It is on the D:

wc00


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

Perhaps this will assisst you. 

wc00


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, boot manager shows "device" partition =C: boot loader shows "device" partition =D: . 
This situation is odd when you only have one partition it was C: now changed (mysteriously) to D:. I need to have a play and see what happens I am concerned you could end up having no choice but to Format. I wonder if a chkdsk on the C: and D: drives would help, use the R parameter.... If we point the boot manager to D: maybe it will boot, then the OS will be on D: drive, as it appears to be now, if we change the entries to C: then no OS is going to be found.


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

Please explain " I need to have a play".


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, sorry I mean from my end, try, test and gauge response done on a test machine, I do not want to give you advice that will force a format, although this still may be necessary.


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

Thanks for the clairification. 

Do you want me to run chkdsk /r ?

What thoughts have you on diskpart? 
#10 at change drive letter in bios? - Slickdeals.net


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, My first advice is to back up all the data you want to keep then you can try the disKpart.

Although the boot manager\loader problem will be the same. So either use the cmds in the link or use bcdedit to change the C drive to D drive in the boot manager, then I expect windows will boot. Once there we can use the MountedDevices in the HKLM registry to change drive letters back to c and then change the boot to c, either way if the problem (and we don't know what caused this) is something else then a format may be the only way.

This can happen on a partitioned drive however you say there was only one partition that's why I am concerned about how to proceed, never seen this before.


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

Thanks for the reply. 

I've cloned the drive. Thanks for the caution. 

What command do you suggest that I use, in bcdedit? 

Please educate me. 

Thanks.


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, I have no idea how you can have an identifier that refers to device c: and the same that refers to device D: in a single partition... so bcdedit needs to know which unique identifier to use. You might find this from the following cmd from within the RE 

bcdedit /enum all /v (press enter), in order to set the change we need to know the identifier, how device os is D: on boot manager and device os on boot loader is C: in the same partition is something I have never seen. Me I would format, might be the safest way, this could be a malware incident.


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

Thanks, j. 

Yes, I have considered malware. 

I'll run the bcdedit command you mentioned & attach a .jpg .


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

j:

Per your request.

I hope the images are viewable.


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

If the information is blurred, just indicate the filename.jpg & the descriptor / category, on the left, OR some other method which you prefer. 

Thanks, j, for your help.


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi well I am not sure so check the identifier, in the re :-

bcdedit /set {9dea862c-5cdd-4e70-acc1-f32b344d4795} device partition=d: (press enter) Restart see how you go


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

j:
I want to be sure that I understand. 

NO offense to you is intended. 

Why "device partition=d" and not "device partition=c"?

Thanks.


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, well the OS from your posts is seen as being on D if we point the partition to C it will not boot , what we are doing has no effect on the drive letter that the OS is on, only the ability to boot to the OS, so we are trying to have both boot manager and boot loader point to the OS drive letter D, the one you say has the OS on it. I said before this situation is something I have not seen, one partition, one drive, two drive letters? If we can get into windows then we should be able to change the drive letter back to C then use either the repair option in seven or the bootrec /fixmbr
bootrec /fixboot
bootrec /rebuildbcd cmds... uncharted waters as I said, you may still have to format.


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

j:
Thanks. 

Yes, I understand that we are in uncharted waters; that this issue is one you had not previously encountered. 

Guess what? NEITHER had I!  [ BIG GRIN ]
No offense is intended, j. I'm trying to find some humor in this trying situation. 
Get the pun?


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

And the answer is [ drum roll please ] 

NUTS (

Booted to the Windows Splash Screen
auto reboot

Rebooted 
F8
selected "disable auto restart"

BSOD
STOP: c000021A [ {Fatal System Errror}
same as #4, above

I've attached the .jpg so that you can verify, if you desire, that I entered the command correctly.

Is it time for diskpart?

Best wished, j.


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, I just went through this again and I think the penny's dropped. The RE has assigned you a drive letter as D for the OS (this is usually ok as it is only the ram drive) however it has also assigned the "boot loader" D.

So what I proposed you do most likely will not work so in my post #18 that should be partition C (or if you haven't touched it leave it as is which is C this is the "boot manager")

Now use the bcdedit cmd to change the os device in the "boot loader" to C, it is currently D. I can not read the identifier you should be able to I think it begins with {e366e7a6... 

bcdedit /set {e366e7a6... device partition=c: (press enter) Restart see how you go

*EDIT* I was writing this as you just posted so give this a try, if it fails I would not bother with diskpart , just format .


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

I ran diskpart. 

diskpart

d:

list volume

select volume D: 

active

exit diskpart

exit cmd prompt

reboot to repair utility

C:\> dir
contains program files
Windows 
users

c:\> bootrec /fixmbr
c:\> bootrec /fixboot
c:\> bootrec /rebuildbcd
each completed successfully

reboot

Msg: no boot mgr

argh

boot to W7 DVD
select repair

Msg similar to: Windows found problems that it can fix 
Reboot 

Bootmgr is missing

reboot to W7 DVD

c:\> bootrec /fixmbr
c:\> bootrec /fixboot
c:\> bootrec /rebuildbcd
each completed successfully

reboot

BOOTMGR is missing


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

reboot to W7 DVD

repair environment

I selected a restore point createed by the system, date PRIOR to onset of problem

System Restore failed to extract the file (C:\) from teh restore point.
An unspecified error occurred during System REstoer. (0x8000ffff)

Different restore point selected.
Same error message

Bootmgr is missing

Boot to W7 repair

Command prompt

c:\> bootrec /fixmbr
c:\> bootrec /fixboot
c:\> bootrec /rebuildbcd
each completed successfully

This was probably present earlier, but I just noticed it.
Total identified Windows installations: 0
sigh


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## jenae (Jun 17, 2008)

*Re: W7 system partition drive letter changed won't boot*

Hi, I admire your patience, did you try what I suggested in post #23 if you run bcdedit both boot manager and boot loader have to point to C: , after this I would cut my losses and format.


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

I was going to run chkdsk /r , but the repair on the W7 DVD informed me tht it was unable to find a system compatible with the W7 RE. 

Re-format

Re-install

Install went uneventfully. 

I am downloading & installling updates from Msft. 

I will scan at NOD323 / ESET online, slave it into my computer that runs AVG, and check for root kits [ unlikely because this is 64 bit, but still possible. 

Thanks, j, for your time & expertise. 

I hope *I* never need the knowledge I have gained. 

I hope that you *personally* never need that which you have learned, j. 

Sincerely,

wc00


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## wc00 (May 3, 2007)

*Re: W7 system partition drive letter changed won't boot*

j:
YES, I performed the actions you mentioned in #23. 

I didn't see #26 until I had composed #27. 

Best of success, j. 

wc00


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## jenae (Jun 17, 2008)

Hi, thanks for an interesting time, how this occurred is the mystery, very difficult to remote diagnose. I hope your friend appreciates your efforts and dedication on his behalf.


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## i MaRk i (Dec 29, 2009)

Oh, dang i missed it, darn school. well either way I had the same happen to me, here is my thread which i solved it. Only difference i had was that i had a secondary OS to change the registry settings, but there are other ways to do it without a second install.

This goes all the way back near to when i first joined:

http://www.techsupportforum.com/for...drive-letters-from-a-different-os-472867.html

Regards,

Mark


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## jenae (Jun 17, 2008)

Hi, thanks Mark, problem here was the boot loader this should not have had both D and C so even changing the mountedvolume would have left us knowhere. I referenced this in post #12



> "Once there we can use the MountedDevices in the HKLM registry to change drive letters back to c and then change the boot to c, either way if the problem (and we don't know what caused this) is something else then a format may be the only way."


Although in most cases the fix is simple using the method in your link, and the other unusual thing was the single partition, this can happen when there are two or more partitions this one only had one, stuck between c & d... would have loved to know how it happened (could be Malware) Format was probably the only way.


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