can’t find domain when use nslookup

My primary DNS server is Win2k. My secondary DNS server is on Linux RH7.1
When I try nslookup for my domain abc.com
The IP for primary DNS appeared but the message is ” can’t find abc.com : No answer ”
Nslookup can find www.abc.com but cannot find abc.com. What went wrong ?
Also got puzzled when somebody said ” your domain got no reverse ”
Please help.