I have personally run into this issue a few times and I have helped a couple of people debug it. What generally happens is that you set up a test or development box running Vista and IIS7.. everything works fine from http://localhost, but when you try to access it from any other machine, you can't connect to the box at all.
9 times out of 10, the problem is the built in Windows Vista firewall. You need to explicitly enable IIS traffic through your server's firewall.
On the server, go to Control Panel -> Security -> "Allow Programs through Windows Firewall", scroll to the bottom and find "World Wide Web Service" and check the box.
Hope this helps!