I have an almost 6 year old Dell Dimension 8250 and have been having trouble all week with blue screens. However I was always able to get back into Windows. I have been running chkdsk and it found loads of problems with the hard disk. Strange because I run it every month and am diligent about computer housekeeping.
I tried to defrag but it said to run chkdsk again and I did, but then I got the final blue screen which I cannot get past. It says c000021a FATAL SYSTEM ERROR, THE WINDOWS LOGON PROCESS SYSTEM TERMINATED UNEXPECTEDLY WITH A STATUS 0xc0000020 (0x00000000 0x00000000) THE SYSTEM HAS BEEN SHUT DOWN.
I tried to use the Dell reinstallation disk but still the above blue screen came up. I cannot even get in with F5 safe mode. Is this the end and is a new computer on the horizon?
Acting on your advice, I pressed F12 and first selected the diagnostics, and after this was done the computer told me to reboot. It then went back to the blue screen, same as above. I then did it again this time selecting BOOT TO UTILITY PARTITION, it didnt and went straight to the blue screen again. I think you must be right about the bad hard disk drive, thanks for replying.
I HAVE JUST RESOLVED THE SAME PROBLEM ON DELL DIMENSION, SO HOPE IT HELPS YOU - ALSO - I AM NO PC EXPERT AT ALL SO THIS WAS GREAT!
REPAIR WINDOWS FROM REINSTALLATION WINDOWS DISC (NOT RECOVERY MODE)
FOLLOW THE DETAILS IN THE LINK HEREWITH AND FINGERS CROSSED
ALSO, THANKS TO TO GEEKSTOGO, THE OWNER OF THIS SITE AS IT WAS A GODSEND FOR ME, AFTER TRAWLING INTERNET FOR SOLUTIONS.
I have resolved the same error on a Dell Inspiron laptop. I had to go through different routes though to get it bootable past this Blue Screen STOP error though.
My laptop wouldn't boot into Windows, and wouldn't go into any of the Safe Mode - still got the Blue Screen BSOD STOP error, and Last Known Good Configuration didn't work either.
I could however find that my hard drive was still accessible, so I pulled the drive out, and plugged it into an external laptop hard drive SATA enclosure, and did a Norton Ghost backup of my data before I mokeyed with the drive. So now I have backups of my data and my crippled Windows installation that won't boot.
I tried the above geekstogo link, but my installation was Windows XP Home OEM - installed by Dell, so it first of all didn't find the currently installed Windows XP Home to do an "in place upgrade" (non-destructive Windows XP OS files only installation), so I thought I was out of luck.
Then I thought since I can't boot into Windows XP and do any uninstall of software drivers, system restore, program uninstall, I started thinking where/what CAN I do. So I knew I could get into Windows Recovery Console from my other home computer Windows XP Pro bootable disk. So I first thought to perform a "System Restore" from inside the Recovery Console, I noticed most places say be careful following these steps with OEM installations because of the incompatibilties of the Registry Hive or something like that, I then found this page and thought I had nothing to loose to try some of these rollback to System Restore points inside the Recovery Console:
That didn't work either, I tried a few of the restore points on the laptop, and a few of the different files (SAM, SYSTEM, SECURITY(really thought this one would do the trick since the blue screen was mentioning Logon)), and many reboots, all still failed in the end with same Blue Screen.
Then I thought some more and thought to myself what if I rollback from SP3 and let windows put back some older valid versions of the windows XP files, just maybe enough to boot into windows, then I can update back to SP3 and I may be OK. Then this other guy mentioned (http://www.geekstogo.com/forum/Stop-c000021a-fatal-system-error-t225847.html) he had some success rolling back from SP3 with the same flavor of STOP blue screen scenario, so I searched and found how to rollback to SP3 inside Recovery Console, and that did the trick!!!
I didn't have to do the second thing mentioned in this article, just the "batch spuninst.txt"