I came across a nice guide which details all steps you can take to resolve this issue located here. We usually get this BSOD issue on windows 10 because there is an issue with a operating system file such as corruption, file is on a bad sector on the local hard drive, a 3rd party software install has replaced a operating system file. Below is a video on youtube I found which shows you how to resolve this issue.
Resolving The Windows 10 Error 0xc00021a BSOD
On the next screen click on "Troubleshoot"
Next click on "Startup Repair"
The startup repair will now start, Follow the prompts to run the repair and reboot your machine when this program has finished. Hopefully your machine now boots to the windows 10 desktop.
If the startup repair does not work we can run a command which checks for corrupt files and bad sectors on your hard drive. Again insert your windows 10 DVD and boot to it. Click on "Repair Your Computer" > On the next screen click on "Troubleshoot" > Click on "Command Prompt" a black window will now popup type the following in to this window " chkdsk /f /r " with out the " and hit enter. This program will now scan your system for file corruption and bad sectors and will resolve any issues it finds. When this has completed reboot your system to see if this has resolved the issue.
If you are still having issues perform the previous steps again to get to the command prompt and run the below 2 commands.
Both of these commands will check your system for errors and will hopefully resolve the Windows 10 Error 0xc00021a.