What is this port/connector on my laptop?

I have this port on my laptop and I have no idea what is it used for. It's not even listen in the laptop technical specifications. The laptop is a HP Pavillion dv5-1101en.

Here is a larger image showing all the ports on the laptop:

Left to right:

1. D-sub 15 pin (AKA VGA)
2. Unknown port
3. Ethernet
4. HDMI
5. eSATA
6. USB
7. IEEE 1394 (AKA FireWire)