Good morning, I am trying to get a iMac (21.5-inch late 2009) connected to a MacBook Pro (Retina, 15-inch, Mid 2014) to use as it's second monitor. The iMac is pretty old. I have bought 4 cables but am not getting connectivity with any combo. Apple Thunderbolt Cable (2 m) Apple Mini DisplayPort to VGA Adapter Apple Mini DisplayPort to DVI Adapter (Single Link) Apple Mini DisplayPort to Dual-Link DVI Adapter It's looking like a compatibility issue. Does anyone know about the iMac (21.5-inch late 2009) and the kind of cables that existed that worked with it that would still be compatable with the 2014 MacBook Pro? It's for my bosses daughter. So replacing the old computer isn't really an option.