The small gap in between the two ports is by design, because you can only use one port at a time.
That is absolutely *not true* As if you had read his full situation (as well as the one I'm typing this on with the same configuration) it does indeed work with both monitor ports functioning. The physical spacing between the ports is just inconsiderate design, not "by design", if that were the case, he nor I could use both ports simultaneously.
I have the exact same situation, all three show up in Display Properties, with one always greyed out; allowing me to choose any two of the three; i opt for two 24" LCDs on the HDMI and VGA ports; but I too would love to use the internal monitor as a third. This is either a driver limitation or a physical limitation of the chipset which cannot address three monitors; however, I HAVE been able to get imagery on all three in the past being MIRRORED, but not seperately - so while there is physical connectivity, there may not be support for the OS to send separate signals to them.