@ChristianHunter
Welcome to HP support community.
A Clean Boot will allow you to troubleshoot the 0xC000021A error in-depth.
- Boot into your system
- Go to Desktop and click Start
- Press the Windows and R keys to open the Run utility
- Type msconfig
- Press Enter
- Go to the General tab, at the System Configuration window
- Click Selective startup
- Uncheck Load startup items
- Go to Services tab
- Check Hide all Microsoft services
- Click Disable all from the bottom right
- Go to Startup tab
- Disable all services listed there by doing: right-click on each and then click Disable
- Restart the computer.
Uninstall software or drivers
- Restart the computer and press the F8 key before the Windows 8 logo appears. If the F8 key doesn’t work, try the F11 key.
- Click Troubleshoot > Advanced Options > Startup Settings > Restart
- Press the F4 key to boot into Safe Mode

If you have the original disc, you can use it to boot into Safe Mode:
- Insert the disc and reboot the system
- Press any key to boot from the media
- Click Repair your computer

- Click Troubleshoot, then Advanced Options, then Startup Settings, then Restart
- Press F4 to boot into Safe Mode.
You can refer this HP document for more assistance:- Click here
I hope that helps.
To thank me for my efforts to help you, please mark my post as an accepted solution so that it benefits several others.
Cheers.
Sandytechy20
I am an HP Employee