Dual Monitors on XPS 8500 Question

My XPS 8500 was bought a year ago and has not been touched from the basic specs.  I'm bad with computers so bare with me.  On the video card ports there is a DVI port and an HDMI port. The computer automatically comes with a DVI adapter so that my VGA monitor works.  Today I've gotten a second VGA monitor and wanted to plug it in right below the USB ports into that VGA port.  However when doing so the monitor always goes into a sleep/black screen mode and I cannot change it from there.  I have gone into the BIOS and enabled dual monitors already.    Again, the video card DVI port has an adapter plugged in so the VGA monitor works.  However the top VGA port will not let my computer get off a black screen.  Also, when nothing is plugged into the video card port the main other VGA port works, and vice versa, but not together.  Any help would be appreciated. :emotion-1: 

EDIT: So after much searching it seems like running a monitor from both ends is not possible. Instead,if were to buy a HDMI to VGA cable and plug it into my computer would my monitor work? I've heard both responses and some also say I need video cards (which I would since I'd plug it into the video card at bottom).