In Windows

• 1). Log on to an account in Windows XP, Windows Vista or Windows 7.
  
  
• 2). In Windows 7 or Vista, click the "Start" button, type "cmd" and press "Enter" to open the command prompt window. In Windows XP, click "Start, then "Run." Type "cmd" and press "Enter."
  
  
• 3). Type "ipconfig/all" and press Enter.
  
  
• 4). Find the line that starts with "Physical "Address" in the program output. The MAC number appears in that line. For example, "Physical Address. . . 00-1F-3C-D0-44-31."
  
  If your computer has multiple network cards--for example, wireless and Ethernet ones--you will find sections in the output titled "Wireless LAN adapter" and "Ethernet adapter." Each will have its own MAC addresses.
  
  

In Linux

• 1). Click the GNOME menu "Applications" and "Accessories." Then choose "Terminal" to open a command prompt window (terminal) in Linux.
  
  
• 2). If you use RedHat, Fedora Linux, type "/sbin/ipconfig" and press "Enter." If you use Ubuntu, Debian Linux, type "ifconfig" and press "Enter."
  
  
• 3). Find the in the program output line that contains "HWaddr=" followed by characters. Those characters are the MAC address. For example, "HWAaddr=00:1D:D1:6B:B6:42."
  
  

In Mac OS X

• 1). Select "System Preferences" in the Apple menu.
  
  
• 2). Select "Network."
  
  
• 3). Click on the name of the connection, for example "AirPort" or "Ethernet," in the left column.
  
  
• 4). Click the "Advanced" button and then select the tab "Ethernet" or "AirPort."
  
  
• 5). Read the MAC address next to "Ethernet ID:" or "AirPort ID:."