From the command prompt, type the following command:
ipconfig /all
This will give you a list of all network adapters (NICs, Bluetooth devices, connected VPNs, etc.). You are looking for the adapter that is bound to the current IP address of the PC. Once the correct adapter is found, look for the line Physical Address. It should be a Hexidecimal number (0-9, A-F) in the format of XX-XX-XX-XX-XX-XX.