Step 1:
Open up the start menu, and click Run. You should now see the following window.
Step 2:
Type command in the Open: box, and click Okay. If command didn't work try cmd. This will bring up a black command prompt window.
Step 3:
The command prompt may look different on your screen, but it doesn't really matter. Type ipconfig /all in that window, and then press the enter key. This will dISPlay a lot of information. If it scrolls off the top you may need to enlarge the window.
Step 4:
In the list of information that went scrolling by look for the Physical Address. The physical address is the MAC Address of this computer.