|Yes, I agree with Rider. you would be better using a DVI to HDMI converter. |
I am doing just that on my monitor where the the Video output is HDMI and the monitor is DVI. The second monitor is VGA from video card to monitor, Converting them both to VGA doesn't make sense.
Every video card I have seen with both HDMI/DVI and VGA output outputs to both ports. With the correct drivers you can then either duplicates each monitor or you can extend the main monitor onto the other giving you more space to play with,.