How to Fix Error Code 0xc000021a after Windows Update

If you have encountered Error code 0xc000021a with a blue screen of death while Windows Update is doing its thing on reboot, then here are some workarounds to get rid of this.

Corrupt Driver Signature Catalog Files

1. When the systems boots up, press F8 repeatedly until you get the Advanced Boot Option Screen
2. Choose the option “Disable Driver Signature Enforcement”
3. If the system boots up then you most likely have corrupt driver signature catalog files. To check which drivers are not signed you can use sigverif

Corrupt Registry Entries

1. When the systems boots up, press F8 repeatedly until you get the Advanced Boot Option Screen (or boot with a Windows DVD)
2. Choose the Repair Your Computer option
3. Open Command Prompt
4. Replace the SYSTEM and SOFTWARE registry hives by running the following commands (assuming OsDrive as C:\ below but it may differ on your system):
   1. cd C:\Windows\System32\config
   2. ren SYSTEM SYSTEM.old
   3. ren SOFTWARE SOFTWARE.old
   4. copy C:\Windows\System32\config\RegBack\SYSTEM C:\Windows\System32\config\
   5. copy C:\Windows\System32\config\RegBack\SOFTWARE C:\Windows\System32\config\
5. Reboot system

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