Security Event ID 680 in 2003R2 connection

Hello everyone.
Please give me some advice.

If it connects to PC from Windows Server 2003 R2 with using
WNetAddConnection2 API,
Connection is success, but Security Event log (Audit of failure) will be
recorded at a target PC.
(Recoreded Event LogID may be different by each target PC's OS. If target PC
is XP, ID is 680)

I monitored packet and understood that The certification is performed in
login user id of 2003R2.
I am assigning only target PC's user id in WNetAddConnection2. Why these
certification is performed ?
When connecting in XP, such an certification is not carried out and the
Event log is not recorded.

Is the output of this Security Event log (Audit of failure) normal ?
Is there a way to stop this event log ?