There is a great online resource that will help you install the correct driver for Windows 2000, as well as walk you through installing the GPIB card. You can find this resource at:
http://www.ni.com/support/gpib/
From this page, just select your operating system and board, and instructions specific to your setup will be generated. It is important to note that you need to uninstall any older GPIB drivers (NI-488.2) before you install the new driver. Version 1.60 or later is required for a Windows 2000 machine.