I have the following iMac: Apple - 21.5" iMac® - Intel Core i5 (1.6GHz) - 8GB Memory - 1TB Hard Drive - Silver It's the latest entry level model currently. I'm wanting to run a second display, I have a decent second monitor that only has a VGA input. So I bought this cable: http://www.amazon.com/gp/product/B013G4EQ9C I put it in one of my Thunderbolt ports in the back of my iMac and the VGA end into the monitor. When I turn the monitor on it says Input Type Not Supported. The cable says its compatible with Thunderbolt, is there something simple I'm missing here? Isn't my iMac capable of running a second monitor?