Event Details
Operating System->Microsoft Windows->Built-in logs->Windows 2000-2003->Security Log->Logon/Logoff->EventID 529 - Logon Failure - Unknown user name or bad password [Win 2000 / XP]
EventID 529 - Logon Failure - Unknown user name or bad password [Win 2000 / XP]
Indicates that a user failed to log on due to unknown user name or bad password.

The person with administrative rights for the computer should establish a threshold limit for attempted log ons. Attempts in excess of the limit should be investigated as a possible attempt to break into the computer

For explanation of the values of some fields please refer to the corresponding links below:

Find more information about this event on ultimatewindowssecurity.com.

Corresponding events on other OS versions:

Windows 2003
Windows 2008
        Event Type:     Failure Audit
        Event Source:   Security
        Event Category: Logon/Logoff
        Event ID:       529
        Date:           11/13/2009
        Time:           11:33:21
        User:           NT AUTHORITY\SYSTEM
        Computer:       DCCC1
        Logon Failure:
        Reason:		Unknown user name or bad password
        User Name:	Paul
        Domain:		LOGISTICS
        Logon Type:	2
        Logon Process:	seclogon
        Authentication Package:	Negotiate
        Workstation Name:	DCCC1
Log Type: Windows Event Log
 Uniquely Identified By:
Log Name: Security
Filtering Field Equals to Value
OSVersion Windows 2000
Windows XP
Source Security
Category Logon/Logoff
EventId 529
Field Matching
FieldDescriptionStored inSample Value
DateTime Date/Time of event origination in GMT format. DateTime 10.10.2000 19:00:00
Source Name of an Application or System Service originating the event. Source Security
Type Warning, Information, Error, Success, Failure, etc. Type Success
User Domain\Account name of user/service/computer initiating event. User RESEARCH\Alebovsky
Computer Name of server workstation where event was logged. Computer DC1
EventID Numerical ID of event. Unique within one Event Source. EventId 576
Description The entire unparsed event message. Description Special privileges assigned to new logon.
Log Name The name of the event log (e.g. Application, Security, System, etc.) LogName Security
Category A name for a subclass of events within the same Event Source. Category Logon/Logoff
Domain Domain of the account for which logon is requested. InsertionString2 RESEARCH
User Name Account name of the user logging in InsertionString1 Paul
Logon Type Interactive, Network, Batch, etc. Please find the code descriptions here. InsertionString3 2
Logon Process The program executable that processed the logon. Please find full logon processes list here. InsertionString4 seclogon
Authentication Package The name of the authentication package (method) used to check user credentials (e.g. NTLM or Kerberos). Please find full authentication packages list here. InsertionString5 Negotiate
Workstation Name The NetBIOS name of the remote computer that originated the logon request InsertionString6 DCCC1
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