So I am trying to setup 3 Monitors for my main desktop computer and I am having some problems. My motherboard is an ASUS M4A785TD-V EVO, and it has integrated graphics on the board. Now, since the integrated graphica can only output to two monitors I bought a discrete video card, the ASUS HD 5450, to display the third monitor. So I installed the card and plugged in all my monitor (Main monitor is DVI, and the other 2 are VGA) I plugged the DVI, and one VGA into the Discrete card, and the other VGA into the motherboards VGA, and I cannot get the one plugged into the motherboard to display anything. Windows will pickup all three but when I try to make any changes to the one plugged into the integrated graphics it gives me this error, "Unable to save display settings" however it does recognize it is there, it recognizes it as "Display device on: VGA". I'm really stuck here and can't figure out what to do from here, also I am running Windows 7 Ultimate 64bit.
I am not sure you can do that with integrated graphics. In fact I am fairly certain you need to take the source from the same video card. What I do know is for Eyefinity 3 monitor setup you need at least one monitor driven by display port. I also think you would need a better card than the HD 5450.
So to summarize, for 3 monitor setup you need a video card with one dual link DVI and at least one display port. Also keep in mind this is increasing your resolution by quite a lot and you'll need a powerful card to handle gaming at this resolution.