Changing the MAC address of a network adaptor NIC
By default the majority of PC and server network adaptors (NIC's) have a built in hardware address (MAC address). This also applies for Virtual PC's and Server's. If the default MAC address needs to be changed for any reason, then this can be changed within the Network Connection Properties within Windows. This is especially useful when networking virtual PC's and servers, where hardware address conflicts can occur.
To specify a custom MAC address, perform the following actions:
1. Go to Start > Control Panel > Network Connections
2. Double Click the network connection that needs the MAC address changing, to open the network connection status.
3. Click properties to open the connection properties.
4. Click Configure, which is just below the network adaptor name. This will open the Network Connection Properties.
5. Select the Advanced tab.
6. In the Property list, select Locally Administered Address.
7. Select the Value field and enter a 12 digit hexadecimal address for the MAC address. Do not use any spaces or hyphens.
8. Click Ok to save the setting and the Mac address should now be configured.