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Windows 7: SFC / Verification of known DLL failed

07 Mar 2011   #1

Windows 7 x64
SFC / Verification of known DLL failed


One morning my Windows 7 x64 system failed to boot. It halts with a BSOD: Verification of a KnownDLL failed

System Repair, System Restore, Last Known Good Config and Safe Mode don't work. I've installed another Windows 7 on a second HDD and would like to fix the first install.
Hardware: Q9450, 8 gb RAM, 1 tb HDD. The Windows install is less than two years old.
Can someone help with this?

I run sfc but I can't find the log. It's not in F:\Windows\Logs\CBS\CBS.log (or C:\Windows\Logs\CBS\CBS.log)
How do I find out what's wrong?

>sfc /scannow /offbootdir=f:\ /offwindir=f:\windows

Beginning system scan. This process will take some time.

Windows Resource Protection found corrupt files but was unable to fix some of them.
Details are included in the CBS.Log windir\Logs\CBS\CBS.log. For example C:\Windows\Logs\CBS\CBS.log

My System SpecsSystem Spec

08 Mar 2011   #2
Microsoft MVP


You're going to have to root around in each hard drive and look for the log files by finding each Windows directory.
Then you have to match the time in the log files with the time that you ran the SFC.exe scan to see if you have the correct one.

I'm not familiar with the syntax that you're using for the sfc - where did you get that from?
My System SpecsSystem Spec
08 Mar 2011   #3

Windows 7 x64

sfc /?
I've checked both Windows\Logs\CBS but no log.
My System SpecsSystem Spec

14 Mar 2011   #4

Windows 7 x64

My System SpecsSystem Spec
16 Mar 2011   #5
Microsoft MVP


If you can't find the log, then we can't tell what the issue is.
Try rooting around in the Event Viewer logs for errors (if you can get into them).
Beyond that, try a repair install (if you can get into Windows): Repair Install
My System SpecsSystem Spec
16 Mar 2011   #6

Windows 7 x64

The log does not exist (at the normal location). Event Viewer doesn't show anything interesting.
How do I find out why the log isn't created properly?
I can't boot that Windows install, so I can'd do a repair install. Why does a repair install require a 'working' Windows anyway?
My System SpecsSystem Spec
16 Mar 2011   #7
Microsoft MVP


If you can't boot to Windows, there's not much hope. You can spend weeks searching out possible fixes and trying them - but I've never had any luck that way.

The place to look for problems with SFC.EXE is the Event Viewer logs - and since there's nothing there it seems to be a Windows problem (IMO)

My suggestion is to gather your reinstallation disks, backup your stuff, wipe the hard drive with DBAN or KillDisk (both are free), and then reinstall Windows clean (without any extra programs and with all updates)
My System SpecsSystem Spec
16 Mar 2011   #8

Windows 7 x64

I've already done that and am running it on a second HDD. It just sucks to have a Windows install die like this.

Why can't you do a repair install when booting from the DVD?
My System SpecsSystem Spec
16 Mar 2011   #9
Microsoft MVP


I dunno - Microsoft hard coded it into Windows starting with Vista and AFAIK there's no way around it.
FWIW - I've only done 2 repair installs and I'm at a 50% success rate - so I wonder if it's that much of a benefit.
My System SpecsSystem Spec
17 Jun 2012   #10

Windows 7 Professional x64

This is for documenting purposes:

To fix the problem,
  1. Go into Windows Recovery by inserting the Windows 7 CD and boot from CD
  2. Then choose Repair (no effect as repair will fail, but wait for it to complete, then...) > select Advance, command prompt
  3. Then get the previous registry backup using the following command:
    xcopy c:\windows\system32\config\regback c:\windows\system32\config
  4. Restart and select Repair my computer again! It'll work and ask for Restart! Restart and it's cool to go!

Note that this is for failed Windows Update problems. E.g. is when system hung during critical Windows Update.
My System SpecsSystem Spec

 SFC / Verification of known DLL failed

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