A MAC (Media Access Control) address is a unique ID assigned to every internet-connected machine that allows it to be identified when connected to a specific network.

To find the MAC address on your Windows computer:

1. Click on the Start menu in the bottom-left corner of your computer. Select Run or type cmd into the search bar at the bottom of the Start menu to bring up the command prompt.
2. Type ipconfig /all (note the space between the g and /).
3. The MAC address is listed as series of 12 digits, listed as the Physical Address (00:1A:C2:7B:00:47, for example).  Each network adapter (wireless, Ethernet, etc.) has a separate MAC address.

To find the MAC address on your Apple computer:

1. Choose System Preferences from the Apple menu.
2. Select Network.  
3. Choose Airport for the wireless adapter MAC and click Advanced (the MAC address is listed as Airport ID).  
4. Choose Built-in Ethernet and click Advanced and Ethernet (listed as Ethernet ID) for the network cable adapter MAC.