On Windows I think you may have to edit the registry to do it. On most home broadband routers, you can do it from their web-based configuration system.
Sort of. The ISP's DHCP server typically remembers the IP address that it previously assigned to a MAC address. When that MAC address requests an IP address later, it tries to give it the same address if it's still available. So on broadband ISPs, the IP address usually stays the same when the MAC address stays the same.
Barry Margolin, email@example.com Arlington, MA*** PLEASE post questions in newsgroups, not directly to me ***