For christ sakes, use a resolution higher than 800x600, it's 2006.

And you can't make it smaller without the scroll bar on the bottom. Eoff is x wide and it'll always be that wide so if you make the window smaller you'll need to have a scroll bar so you can see all of it.
Oh, switching to classic style will let you shrink the window. But just use a higher resolution your computer can obviously handle it if you can play guild wars.