NtLmSsp and NTLM Security Problem on Windows 2003 Standard Edition

Hello
I Use Windows 2003 Standard Edition , today my friend Password in my system (we use one system) changed I find this audit in my system audit:

Event Type:      Success Audit
Event Source:      Security
Event Category:      Logon/Logoff
Event ID:      540
Date:            5/2/2004
Time:            9:56:27 AM
User:            NT AUTHORITY\ANONYMOUS LOGON
Computer:      NS9
Description:
Successful Network Logon:
       User Name:      
       Domain:            
       Logon ID:            (0x0,0x1AE5F4)
       Logon Type:      3
       Logon Process:      NtLmSsp
       Authentication Package:      NTLM
       Workstation Name:      SRV001
       Logon GUID:      -
       Caller User Name:      -
       Caller Domain:      -
       Caller Logon ID:      -
       Caller Process ID: -
       Transited Services: -
       Source Network Address:      xxx.xxx.xxx.xxx
       Source Port:      0
--------------------
Event Type:      Success Audit
Event Source:      Security
Event Category:      Logon/Logoff
Event ID:      538
Date:            5/2/2004
Time:            9:56:17 AM
User:            NT AUTHORITY\ANONYMOUS LOGON
Computer:      NS9
Description:
User Logoff:
       User Name:      ANONYMOUS LOGON
       Domain:            NT AUTHORITY
       Logon ID:            (0x0,0x234913)
       Logon Type:      3
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.
--------------------
Event Type:      Success Audit
Event Source:      Security
Event Category:      Account Management
Event ID:      627
Date:            5/2/2004
Time:            10:12:40 AM
User:            NT AUTHORITY\ANONYMOUS LOGON
Computer:      NS9
Description:
Change Password Attempt:
       Target Account Name:      Admin123
       Target Domain:      NS9
       Target Account ID:      NS9\Admin123
       Caller User Name:      -
       Caller Domain:      -
       Caller Logon ID:      (0x0,0x3E6)
       Privileges:      -
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.


what is problem that Anonymous User can change Administrator password?!!!

- karaji