I'm just bumping this thread because never seen this problem before.
An Idea:
Forget where to do this in XP but!!!
You could take the MAC address off of your card and hard code. (Manually type in) What the address is.
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In XP you can use the regedit to edit the registry from a GUI or the reg command to edit it from the console, I’ll be using regedit. Information on all your NICs can be found the registry key HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E972-E325-11CE-BFC1-08002bE10318}\ . Under this key you will find a bunch of sub keys labeled as 0000, 00001, 0002 and so forth. We can assume any MAC address we want by finding the key that controls the NIC we want to change, putting in a string value called “NetworkAddress” and setting it to the MAC address we want to use formatted as a twelve digit hex number (example: 000000000001). To find out which key is which we can search through them for the value “DriverDesc” until we find the one that matches the NIC we wish to alter. After you set “NetworkAddress” to the address you want just restart the NIC by disabling it then enabling it (or in the case of PCMCIA cards, just eject and reinsert). You can confirm the MAC address change by using the “getmac” or “ipconfig /all” commands.
http://www.irongeek.com/i.php?page=security/changemac
Source which could be wrong so do a little more research.