MAC stands for “Media Access Control” and is a permanent ID number associated with a computer’s physical Ethernet or wireless (WiFi) network card built into the computer. This number is used to identify computers on a network in addition to the computer’s IP address. The MAC address is often used to identify computers that are part of a large network such as an office building or college computer lab network. No two network cards have the same MAC address.
On Windows based computers
Click on the “Start” menu and click on the “Run” prompt.
Type in “cmd” in the “Run” text box and press “Enter.” A DOS command prompt window appears.
Type in “ipconfig /all” in the command prompt and press “Enter.” Note the space between “ipconfig” and the “/.” A list of items appears within the DOS command prompt. Look for “Physical Address” and view the number next to this item. This is your network card’s MAC address.
Depending on whether you are on a wired or wireless connection at the time of checking this information the MAC address shown will be for whichever network device is in use (Ethernet or WiFi).
On Mac OS based systems
Click on the “Apple” logo in the upper left of the screen. Select the “System Preferences” menu item. Select the “Network” option under “System Preferences.” If you are using a wired connection through an Ethernet cable proceed to Step 2, if you are using a wireless connection proceed to Step 4.
Click on the “Ethernet” tab within the “Network” window. If you do not see this tab look for an item labeled “Advanced” and click on this item and click the “Ethernet” tab when it appears.
Look for an item labeled “Ethernet ID” under the “Ethernet” tab. The number next to this item is your computer’s MAC address.
Click on the “Airport” tab under the “Network” options. Look for “Airport ID” underneath the list of available networks. The number next to “Airport ID” is your MAC address.
Knowledge Base, What is a MAC address: http://kb.iu.edu/data/alfq.html
Coffer.com, How to determine MAC address: http://www.coffer.com/mac_info/