Media Server uses any and all address that are assigned to a machine at the time. Of course, if you only have 1 machine you don't need it.
On the Ip address front...
There are 3 ways to get an IP address:
1) You manually edit the properties of a connection and assign one. Normally known as "static".
2) You are attached to a network that has a DHCP (Dynamic Host Configuration Protocol) server. Most consumer "Broadband Routers" now contain DHCP servers and your ISP most definitely has them.
3) If you don't have a static address assigned and Windows can't find a DHCP server, it assigns one from the 169.254.*.* pool.
So assuming you have more than one machine in the house... On the server machine, if you open a command prompt, and type "ipconfig", you'll get the ip addresses assigned. If you're connected to the internet, you should NOT use the address assigned by the ISP because of the possibility of having your packets routed out to the ISP and back again.
Once you've got the ip address, on a Media Center client, you now get to the server by adding a library in the library manager with a location that looks like this: "m01p://ipaddress:port" substituting the real ip address and port. The port defaults to 80.
If this doesn;t get you working, describe your home network and how you're connected to the internet.