DNS For Windows 2000

I have set up the dns server.

The configurations :

NIC IP Address : 203.126.195.94
Preferred Name DNS : 203.126.195.94
Alternate DNS Server : 165.21.83.88
Domain Name Server : server.dns.ism.com
DNS Host Record : www.dns.ism.com

I used the nslookup and it repsonse all right. I then ping www.dns.ism.com and the result is all right. I ping www.singnet.com.sg and the result is time out

If I switch the Preferred DNS Server in the network icon to 165.21.83.88. Ping www.singnet.com.sgis all right. Ping www.dns.ism.com show unknown host name.

Can I know if I miss any setting ?

Thank you