Your computer has a internal Intel video card. This Is what you are saying along the ATI radeon 5700 let me guess two DVI one HDMI no vga on that card but it is on your computer along your audio outputs and usb Esata ports that's called sli two video card's.
But they will not work together that's because you don't have windows 7 or it is disabled and in the motherboard under the bios setting's, It is a time consuming process and step's. 3 monitor's will work. The operating system has to understand as well as the bios together.
So press f12 for boot setting's if you want to install windows 7. I don't care if it's downloaded from p2p sites. Drivers has to be installed use windows update manually download them or www.Intel.com or www.AMD.com this may very to depending on your computer's hardware I recommend windows update for drivers.
But first there should be options under f2 in your bios, Make sure before your drivers are installed it is disabled the dual video or sli it will names every bios work's different and can be updated use the ATI only during installation.
Use windows update to find drivers than restart press f2 than search around under advanced or display for enabled and disabled features enable it's auto or disabled auto mean sli can work use auto or enable press f10 save configuration and restart install the Intel driver restart i take it still not working right 2 last steps restart press f2 disable press f10 save configuration and restart press f2 auto or enable what ever you see will work save configuration and restart boot type your pass word or log in basically right any where on your desktop click screen resolution all 3 should be there.
If it worked good it's tricky but what just did is trick the binary code to make it work. But sorry the ati does not have vga it has dvi to vga converter adapter you intel uses vga and should have a plastic cap with circle and a line this mean do not use but can be used it's called sli. ati it's self can not run but two monitors enabling sli is a hassle