MAC address is sort of serial number of a network card. This MAC address is unique, and so identifies the network card you have installed in your computer.
The MAC address itself is a 12-digit number that also includes the letters A through F. It will appear like this: A2:28:F4:75:B8:CE
Why MAC address?
This is used to identify Wi-Fi networks to recognize it. Some wireless networks will restrict access to only computers that are known. The only way to know a computer is through its MAC address. If you don’t know your computer MAC address, there is an easy way to find it.
MAC address under Windows XP
Click on the Start Menu
Click on ‘Run’
Type cmd and press Enter.
At the command prompt, type ipconfig /all
Alternatively, if using Windows XP, you can use the command getmac.
Your MAC Address is listed under ‘Physical Address’ as a series of 6 groups of two digits, letters and numbers, separated by dashes. Make sure you get the physical address of the correct network adapter – usually there are several listed.
MAC address in Windows 7/2008/Vista
Open a Command Prompt window by clicking the Start button, clicking Programs or All Programs, clicking Accessories, and then clicking Command Prompt.
In the Command Prompt window type getmac (or getmac /v if your computer has more than one network adapter).
MAC address is listed as six groups of two hexadecimal digits, separated by hyphens (-) in the beginning of the line.
If you have more one network adapter and struggling to identify your MAC use this way
Step 1: Click the Start menu and then select Control Panel to open it. The Control Panel menu is displayed.
Step 2: From the Control Panel menu, select Network Sharing Center.
Step 3: Find the link labeled View Status and click it. This will open up a dialog box titled Wireless Network Connection Status.
Step 4: Click the Details button. Find the computer’s MAC address (labeled as Physical Address) and write down that number for future use.