Hi guys, im newbie to this, so..please understand my lack of knowledge. ( also my english )

I just installed IIS on a machine here at home, just to maintain a personal site, and testing the pages im doing, nothing serious or comercial.
The Pc is self alone, so, its over a separated network and connection ( no harm done if attacked lol... ) of my other pcs.
But IIS is giving me problems when i put the IP adress instead of the http://localhost .
If i make http://localhost it opens the 2 normal pages ( when we dont have a default.asp or whatever ), but if its http:// IP... it ask´s me for a username and a password, and i never got of it, a get that error HTTP 401.2 .
And if i try open a sub dir on the server say http://IP.../me/fotos.asp it displays the username and pass again and the error is HTTP 401.3 Access denied by ACL ...

How can i solve this?!