Connect 4 monitors to XPS 8500 w/ AMD Radeon HD 7770 video card

I have a Dell XPS 8500 with a AMD Radeon HD 7770 video card.  I'd like to connect 4 monitors (each has VGA/DVI outputs). I was told when I bought it that I could use 4 monitors with no extra hardware, but I'm having a tough time getting the 4th monitor to work.  I have 3 working fine, but the 4th I cannot get to work.  

When calling in the past I've been told the video card can only support 3 monitors, but that the motherboard has a VGA port which I can use.  I did notice that port is there.  I took the cover off and followed the below instructions to attempt to enable that on-board VGA port:

1. Enter System Setup

2. Go to 'Advanced' ->'Onboard Device Configuration'

3. Select 'Intel Multi-Display', select 'Enable', then Enter 4. Save and exit.

I performed those steps and the monitor connected there is never recognized by Windows 7. 

Any thoughts?

Thanks,

Brian