Vanishing MAC Address

I have an issue with my PC running XP Pro with SP2 and my wireless card.
Somewhere along the line I have lost the MAC address on my wireless card,
but only on my PC. The hardware is a Sony VIAO and a Sony PCWA-C150S. This
problem began a few weeks ago and the unit funtions fine in other PC's. I
have tried to reinstall the drivers many times with no luck. I believe the
issue has to do with Windows and some Networking something.
If anyone can shed some light on this issue for me and a solution to it I
would greatly apprectiate it.

Thanks.