When a Windows 2000 DNS client sends a request, the entry is serviced by the client-side cache, until the TTL has expired.

This can give the impression that 'round robin' isn't occuring.

To view the client-side DNS cache, type: ipconfig /displaydns

To flush the cache, type: ipconfig /flushdns

While you can't disable the cache, you can set TTL to 1:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters

Edit or Add Value name MaxCacheEntryTtlLimit, a type REG_DWORD, and set the data value to 1.