What is a MAC address?

Every network adapter has a Media Access Control (MAC) address, which is a numerical identifier of this device. For Ethernet adapters, MAC addresses are 48-bit values expressed as twelve hexadecimal digits, usually divided into colon- or dash-separated pairs: for example, 00-01-03-E7-A4-02. MAC addresses are also referred to as Ethernet addresses or hardware addresses. The first 24 bits of the MAC address is a hardware vendor-specific prefix called an Organizationally Unique Identifier (OUI). Knowing OUIs can be helpful if you have to find out which device corresponds to a specific MAC address. OUIs are assigned by the IEEE, which maintains the database of OUI-to-vendor mappings.

If you do not know your computer's MAC address, execute the command

C:\>
C:\> ipconfig /all

in the command prompt of MS Windows NT, 2000, or XP. You can also save this information to a text file (address.txt):

C:\>
C:\> ipconfig /all > address.txt

What if my computer has several network cards?

This is not a problem. Each network card has its own MAC address. The software will automatically detect all of them, and will use the registered MAC address (the one you specified in the license agreement form), ignoring the MAC addresses of all other network adapters.