Yesterday I tried to reinstall Snow Leopard on my Mac mini 2009. When I inserted SL DVD (get one with mini) mini doesn't seemed to recognized it. It just loads and spin it few minutes and eject it after 2-3 min. Also no DVD option in "Startup disk" menu. I was 99% that my SL DVD was corrupted (too scratched) and buy new Retail version in Apple store. When I came home and try to load Retail DVD I have the same issues. I tried my friend's SL DVD and his copy loads with no problem at all. I just cannot install SL because DVD wasn't retail. Now I don't know what to do. Any idea what would be the cause? I don't think my mini's DVD unit is broken because I can read and burn other DVD's with no problems. I hope I was clear and sorry for bad english.