You need to set the container div to be width you want the box to be displayed.
Then create another div and nest it within the container, set the width of this one as 4400px or whatever you want.
Make sure you specify overflow:auto for the container but you don't have to bother writing overflow-y:hidden it does it automatically.
Code:
#container {
position: absolute;
Top:170px;
width:1300px;
height: 500px;
overflow:auto;
padding-top:10px;
padding-bottom:10px;
margin-left:20px;
margin-right:20px;
}
#inner
{width:4400px;
height:500px;
}