First sitecollection in the web application is not opening

hi all,

i am just starting sharepoint studies , normally when i create a web application using central administration it works but when i add a host and gave

the same port ( 80 ) of other  web application and add a host name it wont work. I have logged onto the DC and opened the inetmgr and added the name and IP address off the other system where the sharepoint lies. but the sharepoint wont open.

Regards