If your network is fairly small, you can generate the PC's MAC address by typing the following at the DOS prompt(MAC is NIC dependent, not user dependent):
example: f:\nlist user=butkus /a
This will give you the address node and the MAC address(node). You can then redirect the results to either a printer or a text file by doing the following:
example: f:\nlist user=butkus /a >lpt1, or >bkusmac.txt
(there may be a way to list using nlist, and redirect to file, all users but I rarely use nlist. Play with the switches
If you have many users, you are better off using a Netware compatible audit software package such as Visual Audit Pro written by VisionSoft. Unlimited user version is in the $500 range and provides exhaustive hardware & software audit functions across the wire.
Hope this helps.