Just been starting to play with WCF again, and was experimenting with the IIS activation. With IIS7 on Vista, I was getting a 404 error on my .svc file. Since I knew the file existed, I guessed this was probably down to the appropriate handlers not being installed, and since it's not one of the few types that get served as static pages, IIS returned a 404.

I quick poke around the new IIS admin screen showed this to be the case - no handlers were setup to serve .svc files. Turns out that in Vista, this is an optional component that is not installed by default. To get .svc files running, you need to go to Control Panel \ Programs, open the "Turn Windows features on or off" applet and drill into the Microsoft .NET Framework 3.0 node. In there, select the WCF HTTP Activation entry and you should be good to go.