BSOD Fix: STOP: c000021a The Windows Logon Process system process terminated unexpectedly with a status

you get a BSOD like this when you boot your Windows XP:
STOP: c000021a {Fatal System Error}



The Windows Logon Process system process terminated unexpectedly with a status of 0xc0000034 (0x00000000 0x0000000)


The system has been shutdown.
 
Microsoft suggest this article with step-by-step instructions:
http://support.microsoft.com/kb/156669/en-us
 
I've found it easier to fix by booting using ERD Commander 2007 and using the System File Repair Wizard.
it will scan your Windows folder and will repair the corrupted files. the process takes less than 5 minutes and you're up and running again.
 
it is advised to run a disk scan like Chkdsk, to make sure the problem didn't raised because of a HD problem. in most cases the cause is unsuccessful updates/installations.
 
Good Luck,
Yaron

How To Debug BSOD Blue Screen Errors using BlueScreenView Utility

A new tool from the home of Nirsoft has come to the rescue.
Using BlueScreenView, a small portable debugging tool, you can easily find information regarding your previous Stop errors (also known as Blue Screen of Death).
The tool uses the saved memory dump files that Windows saves in the folder C:\Windows\MiniDump\

After running the tool you'll see a table listing each memory dump info including: date & time of crash, the Error Code and parameters and most important- the suspected driver/cause of the crash.

One small extra is the ability to change the detail view into a Blue-Screen simulation screen that shows you how the error message approximately looked like:

Why using this tool instead of the Windows Debugging Tools Pack from Microsoft?
1. it doesn't need another installation of external software.
2. it does a batch debug of all mini-dump files altogether instead of one-by-one using WinDbg.
3. it runs directly from your USB :)

Have fun!

YaronM