I have a macbook core 2 duo 2.0Ghz running the original 10.4 OS. I've read that many have used the $29 disk to upgrade to snow leopard. However, when I start the macbook with the disk inserted, upon startup, the disk is just ejected automatically, before the login screen appears ! Holding C or cmd-opt-shf-del (which normally force boot from disk) did not change anything, which in itself is a bit strange. My disk was purchased in late June 2010. Did Apple recently wised up to disable the disk on 10.4 ?