I have a 21.5" iMac (with Intel processor) that I'm trying to use an external monitor for a new Macbook Pro. Both machines have a thunderbolt input. I bought a Belkin mini displayport to mini displayport connector, but my macbook is not displaying on the iMac. I saw videos online showing this done with the 27" iMac, saying you just needed to press Command+F2, but that is not working for me. I can't seem to find any posts confiming if I can use my 21.5" iMac this way though.