how do i fix "c000021a" error

I receive this error message when my computer boots up:

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

i did some research - i saw some posts on ee for this problem but ive never installed os before so it is a bit confusing. also saw some help on ms:

i guess my question is this - is there an easy or straightforward way for a novice to repair the underlying cause of this error?
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Do you make it into Windows (past the logon screen) before this happens, or before you even get a cance to login?

And have you done any software installs lately?

Does Safe Mode work?

Any MS Updates lately?
eire2008Author Commented:

cant get into windows - the blue screen comes up before the ms loading page gets a chance to.

no software installs lately - the computer has been disconnected from the web, and nothing done locally.

not sure about safe mode

havent updated service pack or anything else from ms since no connection to the web
Try "Safe Mode" or the "Last known good configuration"......

How to perform advanced clean-boot troubleshooting in Windows XP

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If the above suggestions do not resolve it you'll probably find that the quickest and most reliable method is to do a repair install, even though you've never installed one before.

This MS article may help, although the most popular guide appears to be the link by Michael Stevens below>
Reinstallation of XP:;en-us;Q315341

How to Perform a Windows XP Repair Install:

Of interest, but you may have already seen it>
stop c000021a {fatal system error} the windows logon process system process terminated unexpectedly:
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