Internet Explorer 7 does not maximize window’s content

When I expand the size of my IE 7 window it does not expand the content, in other words when I maximize my window, it leaves the web page in the original size with the scroll bars next to it and a big white space between the web page and the actual IE window. I have my resolution set at 1280 x 800, but I have tried reseting my resolution and it still does the same thing. Any help will be greatly appreciated.