Microsoft Knowledge Base Article 830578 contains the following summary:

NBLookup is a command line diagnostic tool that uses the User Datagram Protocol (UDP) to send NetBIOS name queries to Microsoft Windows Internet Naming Service (WINS) servers. NBLookup requires TCP/IP version 4 to run. WINS servers accept name resolution requests on UDP port 137.

NBLookup runs on the following operating systems:

Microsoft Windows NT 4.0
Microsoft Windows 2000
Microsoft Windows XP
Microsoft Windows Server 2003
You can obtain NBLookup from the Microsoft Download Center.

The following file is available for download from the Microsoft Download Center:
Download Download the NBLookupV1.exe package now.

For additional information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base:
119591 How to Obtain Microsoft Support Files from Online Services
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NBLookup can be run in command-line mode, in interactive mode, and in query list mode. The following table contains the correct syntax for each mode.
Mode Syntax
Command-Line nblookup \[-options\] NetBIOS_Name_to_Query
Interactive nblookup \[-options\]
Query List nblookup -ql input_file \[-qr report_file\]