To determine the correct version of the driver to use with your system you can refer to the NI-DAQ Driver Support page as well as the Knowledge Base article NI-DAQ for Windows Support for Different LabVIEW Versions. You will want to choose the newest version which will support all components of your system.
From the first link you will see that the AT-MIO-16XE-50 is supported by the Traditional DAQ driver version 7.4.1 in Windows 2000. In the second link you will see however, that the latest version of the DAQ driver which will install support for LabVIEW 6i or 6.0 is Traditional NI-DAQ 7.1. Therefore this is the version that you will need for your system.
