Error Code oxcoooo21a

Always include exact PC model and version of Windows in your posts.

When do you see that error? Does PC restart and run ok? Or does it just keep crashing and never gets to the desktop?

@Saberross 

This is not the psychic friends network.

Basic information about Windows version, Dell model, what you were doing when the error occurred etc are required.

There are billions of  error codes, such as 0x0000000A, 0x0000003B, 0x000000EF, 0x00000133, 0x000000D1, 0x1000007E, 0xC000021A, 0x0000007B, 0xC000000F

And these are not resolved by remote psychic analysis.

There is support for windows and software but its not free. In your case there are no soft fixes for destroyed Corrupted windows install. 

0xc000021a winlogon.exe & csrss.exe files are corrupted or failing.

0xC000021A is a blue screen of death error that occurs when the Windows user-mode subsystem is compromised. Windows user subsystems are WinLogon or Client Server-Run Time Subsystem (CSRSS). These two subsystems are required components for Windows to function.

There is no fix now only reinstall from DVD or Flash drive onto a new drive.

there are no soft fixes for physically bad hard drives.

ALL drives die. Its not a matter of IF its a matter of when. SSD drives die even sooner when not optimized (they have a maximum number of writes)
This is why I recommend a hard drive first.
Hard drives have Billions of more writes than an ssd and they retain data for 35 years or more in a cool dry place in an antistatic bag with no power.
SSD drives will de trap after 1 year or less depending on the temperature. Once detraped all data is lost.
There is no MBR boot sector this is a UEFI GPT partition.
Its time to remove the old drive and install a new drive clean.
First set F2 BIOS SATA OPERATION TO AHCI NOT RAID OR ATA
Second set F2 BIOS secure boot off.
Use an OEM DVD to F12 boot from.
I suggest you buy one of these NOW because when they are gone they will NEVER BE AVAILABLE AGAIN. In 2025 the iso download for windows will also be gone. Just like it is now for XP/VISTA/7/8
https://www.newegg.com/microsoft-windows-10-pro-64-bit-reinstall-recovery-disc-only-no-license-key-included/p/N82E16832350238
https://www.amazon.com/Seagate-BarraCuda-Internal-Drive-3-5-Inch/dp/B07H2RR55Q
Then recover the data using a dock.
https://www.amazon.com/FIDECO-Dual-Bay-External-Duplicator-Function/dp/B07D6L5CJF

Create Windows 10 usb installation media

Media tool
https://go.microsoft.com/fwlink/?LinkId=691209

https://support.microsoft.com/en-us/topic/microsoft-professional-support-pay-per-incident-faq-575821bc-17bb-7484-4935-334c5437639f

CRITICAL_PROCESS_DIED
SYSTEM_THREAD_EXCEPTION_NOT_HANDLED
IRQL_NOT_LESS_OR_EQUAL
VIDEO_TDR_TIMEOUT_DETECTED
PAGE_FAULT_IN_NONPAGED_AREA
SYSTEM_SERVICE_EXCEPTION
DPC_WATCHDOG_VIOLATION