GET MAC ID

Question

Hi All
i have developed one software and for it's Licensing I used the MAC ID. and it is working fine but for few customers they have Wi-fi adapters and my system is unable to get the mac Id if there is two Ethernet cards LAN and WI-FI so my software license is not working on those pc so please give me the solution that how can i get MAc ID from those PC having two Ethernet cards