Stop C000021a is fatal system error that occurs early in the boot process during initialization with the Session Manager. The status code 0xc000003a indicates STATUS_OBJECT_PATH_NOT_FOUND. You may work around the issue by
disabling integrity checks or by permitting test signing on drivers on boot.
The issue is evidently being caused by a device driver that is corrupt or not
properly signed.
Disabling Driver Signature is of course not an acceptable workaround.
I will describe below a procedure for testing where is the error and of fixing it.
If when following it you encounter any error condition, report it in your post
and do not continue.
Step 1 : Corruption checks
To check for corruption execute the following :
S.M.A.R.T. test to check for general disk failure using a utility such as
Speccy.
For interpreting the results where unclear refer to
this answer.
Run the command chkdsk C:. For more information see
this article,
but in case of error, report to us and do not execute yet any of the repair
options.
Run sfc /scannow to check Windows integrity as described in
this article.
If all tests have passed, continue on.
Step 2 : Locate bad driver
List the drivers as they are being loaded during the boot process in an effort to
determine which driver may be causing the crash, returning driver checks,
by running in an elevated Command Prompt (cmd) the commands:
bcdedit –set sos on
bcdedit /deletevalue nointegritychecks
bcdedit /deletevalue testsigning
Reboot and tell us the name of the last driver to be displayed.
If the name disappears too fast when the crash occurs, film the boot process
using your telephone.
Let us know which driver it is before continuing.
Once the bad driver is identified, you may :
- Disable again Driver Signature Verification and boot
- Enter Device Manager and locate the faulty device
- Right-click it and choose
Uninstall device
- Depending on the driver, you may be given the choice of deleting it,
but wait for our OK
- Return Driver Signature Verification and reboot
- If this works but the related device doesn't work any more,
you may need to download a driver from the manufacturer's website.
If the above has not helped, continue on.
Step 3 : Take backups
Disable again Driver Signature Verification and boot to save all your files.
I also suggest that you take as backup an image of the system disk on some external disk.
My favorite product is
AOMEI Backupper freeware.
If you use AOMEI, create an AOMEI Bootable Disc or USB as
described here,
boot it and verify that it can see your backup, just in case.
Step 4 : Repair Windows
Disable again Driver Signature Verification and boot into Windows.
Do a Repair Install from your boot media as
described here.
It is important to use a boot media that corresponds to your service-pack level (SP1?).
This will conserve your applications and drivers and most system settings.
If Windows can then boot with Driver Signature Verification enabled,
then all is fine. Execute Windows Update repeatedly until all updates are done.
Otherwise, you are in trouble and need to reinstall Windows from scratch.
Best Answer
Sounds like there is a physical disk error on your hard drive.
Also sounds like one of the following things is going on:
The Windows boot process may refuse to continue if boot-time
chkdskreports a physical disk error - in all my years I've never had the pleasure of seeingchkdskreport such an error so I've never experienced this personally but I would suspect it to be the case.The physical error involved may be on a critical system file that Windows needs to run.
The actual error reported by the BSOD may give more clues.
Disk errors can cause sudden slowness in the way you describe. Honestly I would get important data of that drive now by external means and replace it as soon as possible.