Windows 7 Forums
Welcome to Windows 7 Forums. Our forum is dedicated to helping you find support and solutions for any problems regarding your Windows 7 PC be it Dell, HP, Acer, Asus or a custom build. We also provide an extensive Windows 7 tutorial section that covers a wide range of tips and tricks.

Windows 7: BSOD on system boot, cant reach login. cng.sys

17 Sep 2015   #1

Windows 7 Home Premium 64bit
BSOD on system boot, cant reach login. cng.sys

Hi there,

So the other day I booted my computer up like normal and it got halfway through the four windows lights coming together to create the windows logo (after bios boot and just before user login screen) when it flashed with a quick blue screen then rebooted on its own accord. There's no way I can get past this point in the system boot that I've been able to figure out and I was hoping that someone here could help me.

I turned off automatic restart on system failure and it said something about the file cng.sys, so I am thinking that file has become corrupted somehow. Or am I way off. I don't recall installing anything new hardware or software-wise recently and I'm unsure how this happened.

Things I have tried:
Automatic startup repair
Removing CMOS battery and reinserting
Removing individual RAM sticks and trying each of the two separately
Unplugging everything from the back except the mouse and keyboard
Boot to safe mode
Flashing a BIOS Update
Inserting Windows 7 CD and doing a system restore and the other repair options on there
SFC scan with the Windows CD

I assembled the computer myself in 2010 sometime and it has
Gigabyte h67ma-ud2h-b3 motherboard
GTX 560
Intel i5 2500
Corsair PSU - 500 watt I think?
card reader
optical drive

It seems I'm able to access the command prompt. Is there a way I can replace the cng.sys file with a good one or is that not something that would work? I am trying to avoid reinstalling windows as there is data that I would like to keep on the drive.

Any help is appreciated.

My System SpecsSystem Spec
19 Sep 2015   #2

Windows 7 Home Premium 64bit

I have since run a chkdsk, but still crashingbat the same point.
Can anyone help me please? I'm at a loss here
My System SpecsSystem Spec
19 Sep 2015   #3

Win7 Ultimate X64

cng.sys is a native windows file if there was a problem with sfc scan should repair it.
What were the results of your sfc scan ?

Have you checked your bios settings ? if you remove the cmos battery all settings will return to default so check everything is correct, there are some settings that if changed would leave your system unbootable for example changing sata mode from IDE to AHCI or vice versa and ram settings if they were manual before ie voltages/frequency
My System SpecsSystem Spec

19 Sep 2015   #4

Windows 7 Home Premium 64bit

Hi Pauly. So I just ran another SFC and this is a picture of the results.
Imgur: The most awesome images on the Internet
Still no startup

I don't know what BIOS settings to change, everything seems pretty much normal and in order. I never changed any voltages to begin with. I'll have another look.

How can I go about accessing that log file from command prompt?

At this stage it looks like I might need a new hard drive, reinstall windows and then recover my files off my current drive. But I'd rather not take that option if possible. Is my drive maybe failing?
My System SpecsSystem Spec
19 Sep 2015   #5

Win7 Ultimate X64

If you navigate to your system drive you will find the log at %root%/windows/logs/cbs/cbs.log which you can then copy to a flash drive from the command prompt. If you can upload that file we can get one of our SFC gurus to hopefully help you out. This may or may not be related to your boot issues.

While you are there navigate to the windows/minidump folder and see if you have any dump files for us to analyse this would help greatly in narrowing down your issue
My System SpecsSystem Spec
20 Sep 2015   #6

Windows 7 Home Premium 64bit

So I tried to copy to a USB in the command prompt but got an access denied error message.

I used this command here:
findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log >"e:\sfcdetails.txt"

I just guessed e drive, but tried f and g also, but they gave a wrong file path error.

I altered from: findstr /c:"[SR]" %windir%\Logs\CBS\CBS.log >"%userprofile%\Desktop\sfcdetails.txt"

Since I obviously can't access the desktop.

I found the original command on this page. SFC /SCANNOW Command - System File Checker

So basically I'm not sure how to access the log file since I can't access the desktop.
My System SpecsSystem Spec
20 Sep 2015   #7

Microsoft Community Contributor Award Recipient

Win 7 x64 Home Premium (and x86 VirtualBox VM)/Win10

Please just post the CBS.log file (compressed)

You shouldn't have a problem copying the CBS.log file - use the following command

COPY C:\Windows\logs\cbs\cbs.log %userprofile%\desktop\cbs.log

That will put it on the desktop (OK - you can't see it at the moment!)

Now hunt for your USB stick - make sure that it contains a recognisable file in the root folder before you insert it on the machine (a Notepad file named TEST.TXT would be good)

run the following commands


Which one works?
Substitute the functional drive letter into the following command (for <drive>)

COPY %userprofile%\desktop\cbs.log <drive>:\CBS.LOG

It would be a good idea to also copy the Persist files, so use this command as well

COPY C:\Windows\Logs\CBS\CBSPersist*.* <drive>:\

Then you can close the machine down, and move the stick back to your functional machine and compress the copies for upload.
My System SpecsSystem Spec
20 Sep 2015   #8

Windows 7 Home Premium 64bit

Hi Noel.

So i finally got the log files with your guidance, thank you. Turns out i needed to be using D:\Windows... instead of C.

I've attached the compressed CBS.log but i'm going to have to give an external link to the persist files since as once all compressed, it added up to ~70mb. I have no idea if that's normal or not.

Persist files are here:
Mega File Upload - Log Files.rar

My System SpecsSystem Spec
21 Sep 2015   #9

Win7 Ultimate X64

That's great a good step forwards, we will have to wait and see what Noel says about the SFC results as I really don't know what I'm looking at but in the mean time did you try recovering the dump files from your machine ? would be good to have as look at these and may give us a better idea of whats causing the crash if its anything other than windows file corruption
My System SpecsSystem Spec
26 Sep 2015   #10

Microsoft Community Contributor Award Recipient

Win 7 x64 Home Premium (and x86 VirtualBox VM)/Win10

Unfortunately the file doesn't contain any useful data
Please upload the C:\Windows\Logs\CBS\ file - you'll have to zip/rar it, since the forum doesn't accept bare cab files.
My System SpecsSystem Spec

 BSOD on system boot, cant reach login. cng.sys

Thread Tools

Similar help and support threads
Thread Forum
Long time until I reach login screen
Hi there, It takes my Packard bell Easynote TX86 about 2 minutes until it reaches to the login screen. It seems to me a very long time. How can I debug this situation. Pleas ask for any informtion and I'll try to give. Thanks!
Performance & Maintenance
Better login speed when system and boot are on separate drives?
My PC dual-boots Windows 7 on each of two separate HDDs. Both drives have their own boot partitions, but only one drive has the system partition. Despite all my attempts to strip down services and fine-tune the performance of both, there is a noticeable lag between login and the appearance of the...
Performance & Maintenance
Two partition of Win7 install but dual boot can only reach one of them
Dear all, I have installed Window 7 in two partitions (on two SSDs), both using UEFI The first installation is working properly (bootable, got the 100Mb and 128MB partitions etc.) After I installed the second partition, I saw the boot menu displaying two entries. But when I hit to boot on the...
Installation & Setup
Can't reach login screen normally, though safemode works.
I talked to a friend of mine who knows about computers, and even he's never seen anything like this. It's pretty simplistic, really. When I turn on my computer, it starts normally at first, but as soon as it would normally play the beginning tune and show the login screen, instead, the musical...
BSOD Help and Support
Windows 7 Home Premium does not reach login screen - reboot cycle
I have had Windows 7 Home Premium (64 bit) installed on my Gateway NV53 laptop. I must note that my laptop dual boots Windows and Ubuntu 10.04 with GRUB 2 as my default bootloader (which employs a chainloader to boot Windows 7). 4 weeks ago, I began experiencing problems with my Windows partition....
General Discussion

Our Sites

Site Links

About Us

Find Us

Windows 7 Forums is an independent web site and has not been authorized, sponsored, or otherwise approved by Microsoft Corporation. "Windows 7" and related materials are trademarks of Microsoft Corp.

Designer Media Ltd

All times are GMT -5. The time now is 17:27.
Twitter Facebook Google+