Here is the safest procedure to know what MAC address your Mac uses:
- start the application "Terminal" (it can be found in the folder "/Applications/Utilities/")
- type "ifconfig"
- followed by a carriage return, there should be a bunch of text. Go back at the top and locate the "en0". For that en0, find the MAC address that should be looking something like 00:3e:e1:be:c7:bd