Event Viewer Security shows Guest logon?

Event Type: Success Audit
Event Source: Security
Event Category: Logon/Logoff
Event ID: 538
Date: 5/11/2006
Time: 1:19:23 PM
User: MOMS\Guest
Computer: MOMS
User Logoff:
User Name: Guest
Domain: MOMS
Logon ID: (0x0,0x3FFDBD)
Logon Type: 3

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Having multiple entries as shown above. Is someone logging on my system as
guest? Running XP Home, DSL with wireless router. Thanks in advance,