Hello every1
,
Well i couldn't keep still when I fixed this one so i decided to register and help you out (
for windows XP SP 2 users only 
)
So basically, it is possible to access the system in safe mode, and open the minidump file and find out which driver or file causes this blue screen "c000021a".
WHY AND HOW
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The faulty file is called "ntoskrnl.exe" and is part of the windows operating sytem. What happened is this: Basically, whenever you go online (Switching your pc on and it connects to the internet OR you plug in your cable/internet connection etc) the OS downloads updates from the internet and tells you later "updates ready for installation". Usually this goes fine, but sometimes it might cause problems. Sometimes updates clash with other software or are downloaded incorrectly due to internet network bandwidth instability or other issues that might cause the download to be corrupt when it download.
HOW TO FIX
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1.) Firstly, start the machine in safe mode. To do this, start the PC up and keep pressing "F8" to open the "Advanced Boot up options" screen. Then select "Safe mode" from the list. Your pc should then start in safemode.
2.)When on the desktop after loading, navigate to
"C:\Windows\prefetch" and delete its entire contents.
3.)Navigate to your "C:\Windows\minidump" directory , change the view to "Details" , and sort the window by "Date Created" so that the recent minidump.dmp file is on top of the list. Then compare the dates of the minidump files and find the last one in the list that has the same "size" as the first one.
4.)Then, open your control panels and open "add and remove programs".
5.)Check the checkbox "Show updates".
6.)Scroll down to "Windows Upates" and find the entry/installation where the date installed is close to the creation date of the mindump files that you have observed in step 3.
7.)Uninstalled said update, there are likely more then 2 (I had to uninstall 12 updates) and confirm requests of system and remember to check the checkbox "Do not restart now" so that you dont have to restart every time when you uninstall one update.
8.)When you are done with all that uninstalling of the updates you will notice (or maybe not) that one installation will have included the "ntoskrnl.exe" file removal which should indicate to you already that you have won
9.)Navigate back into "C:\Windows\Minidump" and delete all the samesized minidump files exept one ,because they contain the same info on the same file/issue.
10.)Now, restart your machine BUT use "F8" again to get to the "Advanced options" like in step 1 with the only difference being that NOW you select "last known good configeration", and let the machine boot in like that now
PREVENTION AND NOT-HAPPEN-AGAIN
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Well the updates as said cause the problem. If you do manual update from the windows update site, it should work fine OR have a CD that already has an updated service pack 3 or 2 that you need.
