I saw the Hak.5 crew posted a script to randomize your MAC address in *nix:
http://www.hak5.org/wiki/MAC_Randomizer%28perl%29
So I figured you would be interested in something that does the same for Window:
MadMACs: MAC Address Spoofing And Host Name Randomizing App For Windows
http://www.irongeek.com/i.php?page=securit...acs-mac-spoofer
Yes, I know there are already good free tools like Mac Makeup that do this for you, but this one also randomizes the host name as well as the MAC (the two main things a DHCP server logs). Also, I tried to make its instillation and startup process easier. Source is included.