I have a new HP 3130 MT desktop PC running Windows 7 Pro x64. Our DHCP server is a Windows 2003 domain controller. In DHCP, I have an IP address reservation for my PC. This is so I can always receive the same dynamic IP address when I boot up. This is useful since I collect firewall logs directly to my PC. Anyhow, this always worked fine until I got the new PC. Now, every once in a while I notice that I don't have my reserved IP address. When I check my PC MAC address, I notice that it changed since the last time I posted it into my DHCP reservation. This causes me to not receive my reserved IP address and I need to update the MAC address again. Why does it keep changing automatically, and how can I make my PC keep the same MAC address?