Subdomain and delegation

[Eduardo sanz-martin]

Hello,

My mycompany.com is managed by bind 9.3.0 dns. I want to delegate a 
xx.mycompany.com subdomain on a Windows 2000 servers.

I added the following lines into mycompany.com (BIND 9.3 DNS):

xx.mycompany.com. IN  NS server1.xx.mycompany.com.
xx.mycompany.com. IN  NS server2.xx.mycompany.com.

server1.xx.mycompany.com.  IN  A 192.168.1.1
server2.xx.mycompany.com.  IN  A 192.168.1.2

It does not work. I check all logs and i can not find any error.
I put this configuration on bind 9.2.x and  it works on bind 9.2.x. Is there 
extra parameter o options that i have to configure on named.conf or ...
What else do I need to do?

Thanks,
Eduardo