Tag Archives: boot

Windows 8.1 Error 0xc00021a

This error is due to a Device Driver that is unsigned. On a Windows 8.1 load failure, it will start up in repair mode. Select Advanced Repair, then select Change Startup Options and press Restart. The system will then provide a menu of startup options. Select Disable Device Signature Verification (Option 7). This will then allow you to boot into Windows 8.1 to remove the offending device.
To determine which device is causing the issue, use the SigVerif.exe program.

In my case, the program was due to an Intel Wireless/Bluetooth driver, which I promptly uninstalled and allowed Windows Update to install a new version.

Signature Verify Result
Signature Verify Result

Stop 0x7b On Windows 7

Windows BSOD 0x7B Inaccessible Boot Device

This is an issue I have run into a few times. It can be as simple as allowing Windows to do an automated ‘Startup Repair’, chkdsk/r and/or SFC (offline mode.) But if this is happening because you just cloned or repaired a damaged disk, you may be suffering from a bad HD driver.
The BIOS usually has 3 SATA operating modes: IDE, AHCI or Raid. Each one, in turn, has its own hardware driver within Windows. During initial installation, Windows determines which mode you are using and disables the unused ones.
The trick is to take the unbootable HD out of the original computer and attach it (internally or USB) to a functioning Host computer. Using the Regedit program on the Host, load the SYSTEM hive from the unbootable drive and set the “Start” value to “0” for these three keys:

(Remember, because you are modifying an external hive, HKEY_LOCAL_MACHINE will be replaced by whatever name you provided when loading the external hive. I named the external System Hive HLM in this example.)


Unload the hive from the Host Regedit and the close Regedit. You can then ‘Safely Remove’ the drive and return it to its original computer.
Before letting the system boot into Windows, go into the BIOS and change the SATA operating mode to one of the 2 other modes (I prefer RAID to AHCI or AHCI to Raid) Save the BIOS settings and try booting.

Anytime you clone a drive that uses Intel iaStor drivers, you will likely notice slow (usually bordering on insanely slow) hard drive performance on the newly cloned drive. Re-install the Intel iaStor drivers.

Stop 0xc000021a on Windows 7

Try 1st: Reboot and use F8 menu to start Windows using the ‘Last Known Good Configuration’

Try 2nd: System Restore – keep trying further back in history…the first try might not work

Try 3rd:

  1. Pull HD and plug into a working system (by USB if required)
  2. check the SOFTWARE hive to make sure it is not corrupt. (Load hive into working computer’s registry editor)
  3. If it is corrupt, unload the hive from the registry editor
  4. go to {BadDrive}\System32\Config folder
  5. Rename existing SOFTWARE file to SOFTWARE.BAD
  6. then look into {BadDrive}\System32\Config\RegBack folder
  7. copy the SOFTWARE file into {BadDrive}\System32\Config
  8. Disconnect {BadDrive} and plug back into original system and try booting