Wrong Domain Call

Hi everyone,
I have a strange problem :
We have a server (Windows Server 2003 SP2.) with domain : WWW.XXX.COM.
(this is the actual name of the server)
Lately i bought another domain WWW.YYY.COM , working on the same server
(with Index.HTM as startpage).
The problem that no matter what i do - when i browse the YYY domain it
goes to the XXX pages. Even more: when i browse to
http://www.YYY.com/index.htm i get blank page.
I created application in the IIS fro each one of them, and even configured
Exchange server with the YYY domain which works fine.
What i should do in the configuration level to browse to my YYY domain?
Thanks
Erez