To deapee:
That's what I said in the first post I made. The ip address that he has is the IP provided by his router. You will not be able to ping that IP because it is hidden to the public. The router's firewall does that for a reason. If he runs IP config on his own machine he will see the ip he has listed in his post but if he wants to view the ip of his router then he'll need to look at Default Gateway.
And like I said before, the fix for the hosts file is for his roomates benefit. If he get's his IP dynamically assigned (by saying IP I mean the router's IP), then he will need a client (and an account) through a company called TZO. They are very inexpensive and they enable dynamic IP's to have webservers run.
To fufengfrank:
Now what you'll have to do after you get set up with TZO is to have your router forward all incoming port requests to port 80 (or whatever port your webserver is listening on) to the ip of your computer (192.162.1.100). This will make all incoming requests to the router's ip forward to your ip where your webserver is. By the way, you'll need to have IIS listen on the ip of your router, not your computer's IP.