Win2K DNS, System Events, logon events

I have auditing of failed logons on a Win2K server which is PDC. Security Log is huge with failed logons which match the DNS registration/deregistration failures in the System event log. System events are all like this:
Registration of the DNS record ‘blah blah’ failed with the following error – DNS server unable to interpret format.
One failure for each default record in DDNS. Failed logons are from the “real” dns server which is ISP provided or blackhole.isu. I don’t have a pure Win2K network and don’t use this servers DNS for resolution – how can I stop this?