Does your graphics card have both VGA and DVI output? If so you may get away with plugging one monitor into each. If not you will need to buy another card.
Once you have windows recognising two monitors you can go to the display settings (control panel) and extend the desktop on to the second monitor.
What this will do is link both screens to make one virtual desktop area. Having done that you can drag your applications from screen to screen or extend across both.
It is great for large excel sheets, editing documents, using software that has floating toolboxes and generally anything that you need a large display area for.