Yup my USB/eSATA port looks exactly like that but has a wider slit at the middle to take the eSATA connector.
So mine is an eSATA connector?
Just to update.
I contacted Acer tech support about this, the woman I spoke to didn't really seem to know much of what I was on about though.
She said the port I'm referring to is a dual firewire/USB Port.
Does this sound right? :S
Usb 3 ports are blue not black.