MACMask is a powerful, yet an easy-to-use utility tool that changes (or masks) a MAC Address of network adapter for Windows NT, 2000, XP, and Server 2003 systems.
Features
It can change (or mask) a MAC Addresses of a network adapter.
It can scan and display all computers existing on LAN.
It can change a MAC addresses to one with a real vendor name.
It can lists mac addresses already used for changing. Of course, it can delete mac addresses.