According to this KB article 64-bit Windows operating systems like Windows Vista 64-bit are not tested or supported for NLM based on FLEXlm/FLEXnet that Autodesk products uses. It doesn't mention Windows Vista 32-bit.
You probably can install and use it anyway if you read between the lines but according to a source at Autodesk "You cannot install it under 64-bit OSs.". If you have tried and it works add a comment. I know Windows Vista 32-bit works.
According to the Autodesk Network Licensing Guide for AutoCAD 2008 and other Autodesk 2008 products:
Make sure that your network license server meets the minimum recommended requirements. See the following table for hardware and software requirements.
Author notes: Update all tables with pertinent Windows Vista and 64-bit content.
Hardware and software requirements for the network license server
Windows 2003 Server Edition
Windows XP Professional, Service Pack 2
Windows 2000 Server Edition
Windows 2000, Service Pack 4
The Network License Manager supports Ethernet network configurations only.
The redundant license server model is supported only on Windows 2000 Server Edition and Windows 2003 Server.
Pentium III or higher
450 Mhz (minimum)
Network interface card
Compatible with existing Ethernet network infrastructure
The Network License Manager supports multiple network interface cards.
The Network License Manager uses TCP packet types.
What is missing in the help file is that Windows Vista 32-bit is an allowed OS for NLM. It does not say anything officially about Windows 2003 Server Service Pack 2 (SP2).