The NETBIOS name is actually your pre-Windows 2000 domain name.
In most cases if your fully qualified domain name is acme.com, then your NETBIOS name would most likely be acme. But in reality your NETBIOS name could be anything you wanted - like 'acmecorp' or 'wileycoyote'.
You find your NETBIOS name in Active Directory Domains and Trusts. Go to the properties of the domain and look for your pre-windows 2000 domain name.
