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Windows 7: can't boot Win7 any more because of BSOD error 0x0000007B

04 Sep 2017   #1

Windows 7 Home Premium 64 bit
can't boot Win7 any more because of BSOD error 0x0000007B

Hi all,

Useless intro:
My username says it all... After spending more than 1,5 days trying to solve the problem on my own, I'm running out of options and ideas. Since I've read many useful posts on this forum, I haven't completely given up hope that you can save me.

The problem in short:
Win7 hang up at shutdown. After waiting for several minutes or hours, I turned the power off. Since then I can't boot Win7 any more. I always get a BSOD at the same time with the same error code 0x0000007B which stands for INACCESSIBLE_BOOT_DEVICE as you probably all know.

The bigger picture:
I have a dual-boot PC with Linux and Win7 so my MBR is in a Linux partition. Linux runs fine and is unaffected by whatever caused the Win7 boot and shutdown problems. On the Win7 side, I have several partitions:
C: OS partition with all the programs
D: for the data
F: is the Win7 boot partition
P: is an 8GB pagefile
Q: is a system recovery partition
My Win7 installation was kept up-to-date, including my antivirus, Firefox, etc.

What I've tried so far in vain:
- I unplugged the SATA and power cable of the HDD and plugged them back in.
- I turned off AHCI in the BIOS settings and reverted to native ATA.
- I ran Startup Repair a dozen times. The first few times it printed the following message:
Root cause found:
Unknown Bugcheck: Bugcheck 101. Parameters = 0x19, 0x0, 0xfffff880009b2180, 0x4.
I must admit I didn't check what this means. After a few runs of the Startup Repair the error message was gone, but the BSOD remained.

- I ran chkdsk on the relevant Win7 partitions C: and F: twice each and found no problems:
chkdsk /F /R C:
chkdsk /F /R F:
- I checked the RAM 5 times with memtest86+ and found no problems. (The Win7 memory check tests passed with the default settings, but hang up at 21% during the more thorough tests. However, this seems to be a known problem of the software, not a RAM problem.)
- I scanned the Win7 partitions C:, D: and F: for viruses with several up-to-date antivirus programs and found no problems.
- Once I entered a dummy entry in BCD by copying the first, I was finally able to access the advanced menu with F8:
* Starting Win7 in safe mode doesn't help: BSOD after successfully loading 2 AVG .sys files
* Turning on the boot log supposed to be stored at C:\Windows\ntbtlog.txt fails: no log with that name anywhere on C: or F:
* Starting Win7 with the last known working config resulted in the same BSOD
- While in the Startup Repair menu I selected recovery: surprisingly, the list of available recovery points only showed the last recovery point even after I selected the option to display all recovery points. I selected the only available recovery point the date of which was consistent with my installation of the patches from the last patching Tuesday. The recovery itself was successful but booting Win7 failed with... you guessed it! the same BSOD.
My second attempt to restore an even earlier version of my Win7 OS only showed one recovery point again and failed with the following message:
An unspecified error occurred during System Restore. (0x8000ffff)

My layman analysis:
I've spent hours trying to repair the PBR, BCD, etc. but I'd say it was a waste of time since it seems the BSOD occurs during the last step of the following boot order list I found on
1. BIOS firmware initialization and self test (Power On Self Test - POST)
2. load and execution of MBR (Master Boot Record) on first disk
3. load and execution of partition boot record (PBR) on active partition
4. load and execution of boot manager \bootmgr from active partition and then display of boot menu (skipped if only one boot entry)
5. load and execution of Windows NT6 loader winload.exe from \Windows\System32 folder
6. load and execution of kernel and drivers
So my assumption would be that at least one of the (essential?) drivers is corrupt and causes the BSOD.

What I haven't tried yet and why:
- I avoided a complete restoration of Win7 based on 6-year old restoration DVDs so far, because I shrank my C: and D: partitions in the meantime to make more room for Linux and I'm afraid the full restoration process will restore their old size without asking me.
- The last(?) resort would be to return Win7 to its default state as it was when I bought my PC. No idea what this option will do with the MBR and Linux partitions...

My questions:
- Could you please confirm that we should focus our attention on the driver loading step?
- Is there a way to find out which driver causes the BSOD? They're not loaded in alphabetical order and I can't get Win7 to write the boot log.
- Alternatively, is there a way to access a Win7 driver repository and overwrite the drivers currently on my HDD, hopefully replacing the faulty driver(s) in the process? Obviously, this would have to be executed from the Startup Repair cmd line or Linux since I can't boot Win7.
- Do you also think using the full restoration DVDs is risky because it will mess up my partitions?

My priorities:
1) Get Win7 to boot without BSOD and shutdown without hangups.
10) Find the root cause of the issue and fix it to prevent further trouble.
100) Understand how it could happen in the first place.

The "I swear I haven't touched anything, really!" FAQ:
- Last OS change: patches from last patching Tuesday, installed successfully
- Recent SW changes: antivirus update for sure, can't remember anything else that could cause such havoc
- Only HW change: increased my RAM from 4 (2 x 2) GB to 8 GB by adding 2 x 2 GB Kingston RAM. This was about six(?) months ago and I didn't notice any problems after the upgrade.

Observations that might confuse you more than they help you:
- I had a handful of BSODs while using Win7 in the last few weeks. The same with hangups at shutdown. But I was always able to boot normally after such errors until the last instance of a hangup at shutdown which apparently caused the current boot problems.
- I couldn't start IE11 when I tried recently: the browser window closed and a smaller download window opened asking me to choose a download from an empty(!) list. That was really weird. However, I've been using Firefox for years so I can't say for sure whether IE11 ever worked...
- I recently observed awful lag after playing games for many hours. However, restarting the game without rebooting helped so it's most probably unrelated.
- I had the following error for years every single time when booting Linux:
ata5: exception Emask 0x1 SAct 0x0 SErr 0x0 action 0x0 t4
ata5: irq_stat 0x40000008

Oddly enough, since I ran all these checks for Win7 I had a few Linux boots without getting the error. However, I never noticed a negative impact in Linux due to this error and my search seems to indicate that it's a problem that could be caused by my old Linux kernel.

Final words:
I apologize for this very long post but I thought that most of the info was relevant and that you'd ask anyway if I didn't provide it. Thanks a lot in advance for your precious insight and help.

My System SpecsSystem Spec
05 Sep 2017   #2

W7 home premium 32bit/W7HP 64bit/w10 tp insider ring

Hi DU,

Im not a BSOD guy,
Do have the following observations tho.

You should never shutdown your comp when updating.
I suspect that when you did it borked AVG, why usually Safe boot driver loading fails on PNP, NOT AVG.

You can repair your system with recovery discs, but your old ones may not have SP1 and they WILL need to be. The other problem it will keep all your progs that includes AVG.
You will need to remove AVG via command mode, even then it might not work as i suspect its corrupt
(if its a paid version AVG could point you in the right direction.)
A repair will not affect your partition sizes unless you manually change them whilst running it.

If you go the clean install route if i was you id redo all my partitions/drives.
(note W7 hates being loaded behind any other OS )

My System SpecsSystem Spec
05 Sep 2017   #3

Windows 7 Home Premium 64 bit

Hi Roy,

Thanks a lot for your input. A few remarks and questions from my side:
  1. I'm 99% sure I did NOT shutdown my PC while AVG (or any other software for that matter) was installing an update. I manually check for AVG updates right after logging in and other programs are set to ask me when updates are available, so they don't start automatically in the background.
  2. PNP = Plug & Play? If so, no need to answer. If not, please correct me.
  3. It looks like my assumption about how recovery works was wrong: I thought it would completely overwrite my OS partition with the old stuff stored on the DVDs. But if I understand you correctly, the recovery process only overwrites Win7 specific files and registries.
  4. I'm afraid my recovery version of Win7 on the DVDs is indeed without SP1. Does it mean recovery won't run because the current broken version and the old recovery version are somehow incompatible?!
  5. If by "behind" you refer to the order on the HDD, then I was aware of that. Therefore, my partitions are in the following order: MBR, Win7 boot (F:), Win7 OS (C:), Win7 data (D:), Win7 pagefile (P:), etc. All the Linux partitions are behind the last Win7 partition.

Next steps for me:
  • Find out more about the drivers AVG free Edition loads at boot time. Try replacing potentially corrupt AVG drivers with valid ones.
  • Try uninstalling AVG from the command line.
  • Try the recovery DVDs.
My System SpecsSystem Spec

05 Sep 2017   #4

Windows 7 Home Premium 64 bit
New BSOD after disabling AVG antivirus

Hi all,

a little update from my latest experiments:
  • Uninstalling the AVG antivirus SW is non-trivial as both the AVG setup binary and AVG_Remover.exe downloaded from AVG's support site refuse to run:
The subsystem needed to support the image type is not present.
  • msiexec.exe seems to run so this might be an option I haven't investigated further.
  • AVG's recommended way to prevent their antivirus SW from loading at boot time if you suspect it to cause problems while booting is the following: rename all AVG drivers from .sys to .old for example
C:\Windows\System32\drivers> rename avg*.sys avg*.old
  • The good news is my previous BSOD is gone and Win7 now loads drivers up to CLASSPNP.sys if I'm not mistaken. I will double-check that tomorrow.
  • The bad news is, of course, that I get a new BSOD...
*** STOP: 0x0000007B (0xFFFFF880009A9928, 0xFFFFFFFFC0000034, 0x0000000000000000, 0x0000000000000000)

I have to go to bed for now, but will check whether the new error message is more helpful than the previous one and whether I can turn on the boot logging tomorrow evening.

My System SpecsSystem Spec

 can't boot Win7 any more because of BSOD error 0x0000007B

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