It looks like the networking rewrite in Vista took out an old (hacky via registry) feature that allowed Windows to do what any other OS allows, assignment of a secondary static IP to a network interface with an active DHCP IP.

Anyone know a way to still do this under Windows 7? My situation is that I want to configure Synergy between my Mac and PC with a static IP to avoid issues with my DHCP IP changing. The DNS servers here aren't the quickest things to update (my IP change from friday still isn't showing up properly), so I figure just hardcoding IPs for Synergy will be the most reliable setup.

Keep in mind the "Alternate Configuration" tab that shows up in the TCP/IP properties is only for setting what IP is used when a DHCP server is unavailable. It isn't for having both a static and DHCP IP active at the same time.