server name for DNS servers

Running DNS for internal addresses on two NetWare 6.5 sp7 servers.
External addresses are handled by our ISPs DNS. Typing nslookup on a
Windows XP PC returns the following.

C:\>nslookup
*** Can't find server name for address x.x.x.x: Non-existent domain
*** Can't find server name for address y.y.y.y: Non-existent domain
*** Default servers are not available
Default Server: UnKnown
Address: x.x.x.x

x.x.x.x and y.y.y.y are my two DNS servers. Why am I getting errors
such as "can't find server name..." and "default servers are not
available"? It looks to me like I have that information specified in
my DNS/DHCP Mgmt Console. Suggestions?

Thanks!
Ken

Novell....it does a server good!