How to fix “STOP: c000021a (Fatal System Error)” Error!” in windows XP

If you have blue screen and this error:

STOP: c000021a {Fatal System Error}
The Windows Logon Process system process terminated unexpectedly with a status of 0xc06d007e (0×00000000 0×00000000).
The system has been shut down.


when you boot your Windows xp, here is a solution how to resolve the error.

0) Copy c:\windows\system32\winlogon.exe from working Windows XP (use Windows xp with same service pack) to your usb drive
1) Boot your computer with some live cd (I used Windows XP Live!)
2) make copy or rename your winlogon.exe file (I renamed it to winlogon.exeold)
3) copy winlogon.exe from usb drive to your \windows\system32\ directory
4) boot windows

if everything is ok, then that is it, however, in my case computer booted, but explorer was not working so used system restore.

5) when Windows loads, go to task manager (with ctrl+alt+delete or ctrl+shift+esc) and run System restore by going to File, Run, and c:\windows\system32\restore\rstrui.exe

Then restore to some old restore point...and thats it :)
p.s. maybe you will need to run

sfc.exe /scannow

to check your system files.