Changing the MAC address on Windows is very easy, all you have to do is to use free MAC spoofing utilities like "Technitium MAC Address Changer", "SMAC" or "EtherChange".
For spoofing MAC Address on Linux computers you will need to use following commands with MAC address of your choice:
# ifconfig eth0 down
# ifconfig eth0 hw ether 00:80:32:AA:c1:40
# ifconfig eth0 up
# ifconfig eth0 |grep HWaddr
For MAC Spoofing on Apple Mac computers follow the instructions provided here.
Download Windows MAC Spoofing Utilities :
* Technitium MAC Address Changer
Source : http://www.megaleecher.net/Spoofing_MAC_Address