I am trying to upgrade my macbook to snow leopard. I have a 2 year old macbook. 2.4 GHz Intel Core 2 Duo. With 2GB 1067 MHz DDR3 and version 10.5.8. I have bought the Snow Leopard CD installer and loaded it up. When i click install Mac OSX a message comes up saying "Mac OS X Snow Leopard cannot be installed on this computer". Does anyone know why? Help please.