dual boot giving different MAC addresses

Here's a puzzling situation:

I ran ifconfig under Linux and gave the reported hardware address for the
NIC to my network administrator. He gave me a static IP and everthing
worked fine.

Then, I booted into Windows 98 and configured the same (and
only) network card with the same IP/gateway info. I can't connect,
apparently because a different MAC address is being reported. I get a
message saying that the MAC address is such-and-such and is in conflict,
etc. etc. I tried to spoof the real (?) MAC address that Linux reported
and which works on the network by changing the card properties. Now
running winipcfg shows the spoofed/"real" address, but the conflict
continues anyway. What the heck is going on here?

John M. Norvell
Department of Anthropology
William James Hall 348
Harvard University
Cambridge, MA 02138