on the Vista machine: go to network, right click and open properties...under the name of your network click on customize and then set to private. Make sure the 1st 3 settings under sharing and discovery are on. Then go to network connections and click on properties and uncheck Internet protocol version 6 and both link layer topologys. Reset your router and restart your machine and you should now be good to go.
hope this helps~!
-JxL
